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Previous work from this laboratory has shown that preimmunization of syngeneic hosts with Rous sarcoma virus (RSV)-transformed cells elicits a strong immune response against the growth of transplantable RSV sarcomas, mediated by T lymphocytes expressing the surface phenotype of helper cell precursors (Prat, Di Renzo & Comoglio, 1983). This paper shows that anti-tumour immunity may be elicited in tumour-bearing animals by triggering an experimentally pre-amplified T-helper cell population at the site of tumour growth. Mice were treated with cyclophosphamide (which inactivates suppressor T cells) followed by skin sensitization to trinitrochlorobenzene (TNCB) according to a protocol that has been shown to induce an appreciably amplified generation of trinitrophenyl (TNP)-reactive helper T cells (Fujiwara et al., 1984). Five weeks after TNCB painting, mice were transplanted s.c. with a lethal dose of RSV-induced syngeneic sarcoma cells; the injection at the tumour site of TNCB induced the regression of the tumour in mice in which the TNP-helper cell population has been amplified, but not in controls, including those injected with a non-related hapten or sensitized to TNCB without inactivation of suppressors. [ABSTRACT FROM AUTHOR]

This paper investigates desensitization in vitro, e.g. the inhibition of the transfer of contact sensitivity to picryl chloride by incubation of the passive transfer population with picrylated spleen cells. It asks whether desensitization is based on the same T-suppressor circuit which is responsible for the inhibition of passive transfer by antigen-specific T-suppressor factor (TsF). In this circuit, the T-suppressor cell which acts at the efferent stage (Ts-eff) makes TsF. This TsF depresses contact sensitivity indirectly by arming a T-acceptor cell (Tacc). The armed Tacc, when exposed to antigen (picrylated spleen cells), liberates a non-specific inhibitor which blocks the transfer of contact sensitivity. The three elements of this T-suppressor circuit occur in nylon wool-purified T cells prepared from the lymph nodes and spleens of mice four days after immunization with picryl chloride. This population transfers contact sensitivity and can be desensitized in vitro. It contains Ts-eff which can be isolated by panning (adherence) on picrylated albumin and detected by their ability to inhibit passive transfer. The 24 hr supernatant of cultures of these cells contains TsF. Finally the population contains Tacc which appear in the spleen 2 days after immunization and virtually disappear by 10 days. Further experiments demonstrated that the Ts-eff and the Tacc were not merely present but actually required for desensitization in vitro. Immune cells depleted of both Ts-eff (by panning on picrylated albumin) and Tacc (by arming with anti-oxazolone TsF and panning on oxazolonated albumin) cannot be desensitized. To restore desensitization both Ts-eff and Tacc must be added back. The Ts-eff were characterized as cyclophosphamide resistant, adult thymectomy sensitive cells (Cyr, ATx5), which adhered to antigen and were produced only by specific immunization. The Tacc were characterized as CF5, ATx5 cells which adhered to antigen only after arming with antigen-specific T-suppressor factor and were produced after immunization with an unrelated contact sensitizer, 'oxazolone'. It was concluded that desensitization in vitro was due to the interaction of two distinct T cells: the T-suppressor cell which acts at the efferent stage of the contact sensitivity reaction and the T-acceptor cell which becomes armed with the specific T-suppressor factor produced by the Ts-eff. [ABSTRACT FROM AUTHOR]

This paper describes a method for in vitro measurement of specific cell-mediated immunity in the mouse. Animals were immunized parenterally with ovalbumin in Freund's incomplete or complete adjuvant, and a direct migration inhibition assay was performed, using lymphoid cells from the draining lymph nodes. Migration inhibition was found to be antigen specific, correlated with systemic delayed-type hypersensitivity measured in vivo by skin testing, and had a high degree of sensitivity for ovalbumin. The migrating cells were identified as lymphocytes. Lymph node lymphocyte migration inhibition provides a reliable in vitro assay for regional CMl in the mouse. [ABSTRACT FROM AUTHOR]

A mean of 6.9 per cent of small lymphocytes in peripheral blood preparations and between 1.8 and 2.4 per cent of small lymphocytes in lymph node, spleen, bone marrow and thymus preparations from unimmunized guinea-pigs bound 125I-labelled purified protein derivative of mammalian tuberculin (mammalian PPD). The percentage of these cells fluctuated but did not alter substantially after immunization with BCG or with BCG emulsified with human thyroglobulin (HTg) in Freund's incomplete adjuvant (FIA). Blocking experiments indicated that the binding of 125I-labelled mammalian PPD was specific and there was tentative evidence that the lymphocyte receptors may be IgG. A comparison is drawn between the observed time course of 125I-labelled mammalian PPD- binding small lymphocytes and the response of lymphocytes sensitive to strong histocompatibility antigens, and it is proposed that the propensity of certain anti- gens to induce a delayed hypersensitivity-type response is related to the presence of substantial numbers of antigen-binding cells in unimmunized animals. A noteworthy incidental finding was an unexplained depression in the cellular and humoral responses to mammalian PPD in guinea-pigs that had been immunized with HTg-BCG-FIA emulsion. [ABSTRACT FROM AUTHOR]

Peripheral lung tissue contains large numbers of T cells, strategically located for immune surveillance at the blood-air interface. Given the intensity of antigenic exposure at this site, it is clear that local T-cell activation events require strict control, in order to maintain tissue homeostasis. How this control is achieved in this unique tissue microenvironment is unknown, and the present study sought to elucidate the process via detailed analysis of the surface phenotypic characteristics of freshly isolated lung T cells. We report below that these cells display typical characteristic of ‘postactivation’, notably elevated basal Ca2+ concentrations, down-modulated T-cell receptors, expression of Ia and ‘late’ activation antigens and concomitant CD4/CD8. However, levels of interleukin-2 receptor and CD2 expression were below those expected of ‘activated’ T-cell populations, and virtually all of the cells were found to be in the G0/G1 phases of the cell cycle. These properties bear a remarkable similarity to those of T cells activated in the presence of endogenous tissue (alveolar) macrophages from the lung (see accompanying paper). We hypothesize that they reflect the in vivo operation of an endogenous macrophage-mediated T-cell anergy-induction process, the function of which is to limit the local clonal expansion of T cells in peripheral lung tissue after in situ activation. [ABSTRACT FROM AUTHOR]

Delayed footpad reaction against syngeneic testicular cells was compared between males and virgin females of C3H/He mice. Mice were immunized subcutaneously with 1 × 107 of syngeneic testicular cells and the reaction was elicited with 1 × 106 of syngeneic testicular cells 6 days after the immunization. When mice were pretreated with 0, 25 or 50 mg/kg of cyclophosphamide (CY), the delayed footpad reaction was detected in female mice, but not in male mice under the same conditions. This sex difference in the reaction to testicular cells was not attributed to the recognition of H-Y antigen by female mice. A sex difference in the reaction to sheep red blood cells (SRBC) was not observed. The sex difference in the reaction to testicular cells was attributed to testicular cells other than sperm because a sex difference was not detected against sperm. The implications of these findings are discussed in relation to the tolerance phenomena of autologous testicular cells. [ABSTRACT FROM AUTHOR]

Lymph node cells from immunized rabbits were cultured with varying concentrations of antigen in preheated (56°, 30 minutes) autologous serum which had been collected before immunization. [3H]Thymidine was present for the last 6 hours of the 24-hour culture period and the radioactive labelling of acid-precipitable material was then determined. Changes in labelling due to variations of culture conditions were interpreted according to whether they were specific for control or antigen-treated cultures or non-specific. Cell concentration and serum concentration were predominantly non-specific variables influencing the labelling in control and antigen-treated cultures to a proportionate extent. However, at serum concentrations below 5 per cent labelling was disproportionately inhibited in antigen-treated cultures; there were further minor disproportionate inhibitions at higher serum concentrations. Labelling was inhibited by increasing the concentration of serum from 25 to 50 per cent, mainly due to a non-diffusible competitive inhibitory activity. Isotope-dilution analysis of the effects of serum on labelling over a wide range of serum concentrations indicated that the relationship was a complex one with at least three step-wise stimulations of the maximum labelling rate being produced by increasing the serum concentrations from 0 to 25 per cent. Labelling in antigentreated cultures containing post-immunization serum was less than labelling in cultures containing an equal volume of preimmunization serum, but labelling in control cultures was enhanced by post-immunization serum. These results are shown to be compatible with the proposals (i) that labelling in control cultures reflects the response of cells to low concentrations of endogenous antigens, and (ii) that preimmunization serum and post-immunization serum contain ‘natural’ and ‘acquired’ antibodies respectively, which normally buffer cell-borne receptor sites against reaction with endogenous and exogenous antigens. [ABSTRACT FROM AUTHOR]

Summary. Rabbit circulating lymphocytes have been examined for the a locus allotypic markers As1, As2 and As3 using the mixed antiglobulin reaction. These determinants cannot be as easily demonstrated as the b locus determinants As4, As5 and As6. Undiluted antiserum is required and even then the percentage of reacting cells is low. The specificity of the reaction was checked by an inhibition procedure. [ABSTRACT FROM AUTHOR]

Waning immunity to mumps after one or two doses of the measles, mumps and rubella (MMR) vaccine has been described. Using a human peripheral blood lymphocyte (PBL)–severe combined immunodeficiency (SCID) mouse model, MMR vaccine recipients with undetectable and high antibody titres against mumps were compared for the presence of circulating mumps-specific memory B cells. Peripheral blood mononuclear cells (PBMC) from six donors (three subjects with undetectable and three with high antibody titres against mumps) were injected into the spleens of non-obese diabetic (NOD)-SCID mice (three mice per subject). Mice were pretreated with TMβ1 and total body irradiation to improve engraftment. In vivo production of human antibodies against mumps was evaluated in mouse plasma on days 7, 10 and 13 with a commercial enzyme-linked immunosorbent assay (ELISA), functional reduction neutralization test. Three donors had mumps antibody titres below the detection limit (titre < 230) and three had high antibody titres (range 5700–7300). None of the mice injected with PBMC from subjects with undetectable antibody titres showed detectable human antibody titres, despite the presence of cell-mediated immunity in two of the three donors. Seven out of nine mice injected with PBMC from subjects with high antibody titres acquired detectable antibody titres for mumps in their plasma. PBMC from vaccinees without detectable serum antibodies against mumps virus were unable to induce secretion of anti-mumps antibodies in the blood of recipient mice, whereas PBMC from vaccinees with high antibody titres were able to do so. This observation suggests that the frequency of mumps-specific memory B cells is very low in vaccinees with undetectable antibody titres. These individuals may therefore be at risk of developing mumps disease upon encounter with wild-type virus. [ABSTRACT FROM AUTHOR]

Hepcidin regulates intracellular iron levels by interacting with and promoting the degradation of ferroportin, a membrane protein and the only known cellular iron exporter. Studies of hepcidin expression and regulation have focused on its effects in innate immunity and as a regulator of systemic iron metabolism. In the present study we characterized the expression of hepcidin messenger RNA (mRNA) in human peripheral blood mononuclear cells (PBMCs) with a focus on peripheral blood lymphocytes (PBLs). We found that (1) all human PBMCs analyzed express basal hepcidin mRNA levels; (2) hepcidin mRNA expression increases after T-lymphocyte activation; (3) expression by PBLs increases in response to challenge by holotransferrin (Fe-TF) and by ferric citrate in vitro; (4) the Fe-TF-mediated up-regulation of hepcidin decreases ferroportin expression at the cytoplasmic membrane of PBLs; and (5) silencing of tumour necrosis factor-α (TNF-α) abrogates the effect of Fe-TF. In summary, we show that hepcidin expression determines intracellular iron levels by regulating the expression of ferroportin, as described in other cells, and that inappropriately low expression of hepcidin impairs normal lymphocyte proliferation. The results establish hepcidin as a new player in lymphocyte biology. [ABSTRACT FROM AUTHOR]

X-irradiated (250 rads) A mice injected with syngeneic trinitrophenylated spleen cells (Syn-TNP-SC) developed syngeneic delayed-type hypersensitivity (Syn-DTH) after footpad challenge with syngeneic concanavalin A-induced lymphoblasts (Syn-Con A blasts), as indicated by footpad swelling and lymph-node proliferation assays. Genetic analysis with different recombinant strains of mouse revealed that the H-2Dd subregion restricts these immunological activities. A small immunogenic entity was isolated from Syn-TNP-SC extract by gel filtration and affinity chromatography with anti-Dd antibody. X-irradiated A mice injected with this antigen also generated inflammatory responses after challenge with Syn-Con A blasts. Analysis of the data obtained from the gel filtration and the affinity chromatography suggest that the Syn-DTH-stimulating antigen is a fragment of the H-Dd heavy chain with a molecular weight (MW) of 5,000 to 10,000. This fragment does not contain TNP molecules or sugar moieties and neither does it express affinity for antibodies against class 11 products. Ltk- cells transfected with the H-2Dd gene also induced Syn-DTH in X-irradiated A mice, while the parent cells failed to stimulate such a response. Taken together these findings indicate that the selection process in the thymus is not absolute and T cells recognizing self-major histocompatibility complex (MHC) products do migrate from this organ to the periphery of the immune system. The possible biological significance of these autoreactive cells is discussed. [ABSTRACT FROM AUTHOR]

We have previously reported that the immunization of BALB/c mice with MOPC-104E myeloma protein (M104E) induced idiotype-sjjecific Ly 1-negative B lymphocytes that had an ability to enhance idiotype-,positive anti-dextran antibody production. It was also shown that the cell interaction between idiotypic and anti-idiotypic B lymphocytes was observed in a class Il-restricted manner. The effect of monoclonal anti-class II antibody on the B-B cell interaction is investigated in this report. The addition of anti-I-A or anti-I-E monoclonal antibody into the B-B cell interaction system, from both BALB/c (H-2d) and BALB.K (H-2k), inhibited the enhanced antibody production mediated by idiotype-immune B lymphocytes. Interestingly, however, it was revealed that the anti-IA and anti-I-E antibodies acted differently on each B-lymphocyte population. Pretreatment of an anti-idiotypic (idiotype-immune) enhancing B-lymphocyte population with anti-I-A antibody diminished its enhancing activity, while anti-I-E did not. On the other hand, pretreatment of dextranimmune antibody producing B cells with anti-I-A antibody showed no effect, while anti-I-E inhibited anti-dextran antibody production. When the enhancing B-lymphocyte population of F1 mice was treated with anti-I-A antibody specific for one of their parents' haplotypes, co-operation with the respective haplotype B cells was inhibited, but the other haplotype was not. The inhibitory effect of anti-class II antibodies could only be seen at the early phase of culture period. Taken together, the results of these experiments suggest that the class II antigens are concemed with the self-recognitive cell interaction among B lymphocytes in the frame of idiotype network systems. [ABSTRACT FROM AUTHOR]

Spleen and mesenteric lymph node cells from Nematospiroides dubius-infected and normal control mice were cultured in vitro with N. dubius antigen. Proliferation of these cells in response to antigen was measured by the uptake of [&3sup;H]TdR. Cells harvested from mice during a primary infection did not proliferate in vitro; however, low levels of specific proliferation could be demonstrated if these mice were treated on Day 5 post-infection with 20 mg/kg of cyclophosphamide i.p. A strong cell proliferative response was measured 6 days following a challenge infection; spleen cells responded more strongly than cells from the mesenteric lymph nodes (M LN), but the addition of lymph node cells to spleen cell cultures did not suppress the latter response. Responsiveness of spleen cells to concanavalin A (Con A) was two-fold higher in infected mice than in normal controls, but the proliferation of MLN cells to Con A was similar in infected and uninfected mice. When N. dubius- resistant B10.BR (H-2k) mice were compared to the susceptible B10.BR (H-2f) mice, no differences were observed in the spleen cell response to N. dubius adult antigen following challenge infections. However, after a tertiary infection, MLN cells from the resistant strain proliferated strongly in comparison to cells from susceptible mice. Spleen or MLN cells from resistant mice transferred immunity to naive recipients provided that the recipients had received a prior injection i.p. with adult N. dubius antigen. The injection alone, or cells in the absence of the injection, failed to protect the recipients from N. dubius challenge. [ABSTRACT FROM AUTHOR]

The mechanism by which a Db-specific helper clone (clone 9) and a hybridoma-derived Db-especific helper factor, referred to as ASHF, induced cytotoxic T lymphocyte (CTL) responses to alloantigens was investigated. Clone 9 or ASHF helped CBA thymocytes to produce CTL against B6 (H-2b), but not D2 (H-2d), alloantigens. However, when BDF1 (H-b,d) spleen cells or an equal mixture of B6 or D2 spleen cells were used as stimulator cells, CTL responses to both B6 and D2 were induced. This suggested that clone 9 cells or ASHF could induce the production of long-ranged, non-antigen-specific helper factor(s) in B6-stimulated cultures. One of these long-ranged factors produced in B6-stimulated cultures was found to be interleukin-2 (IL-2). Thus, clone 9, which is a non-IL-2 producer, increased the production of IL-2 by irradiated B6 spleen cells and by CBA anti-B6 cultures by 4·7- and 5·7-fold, respectively. ASHF did not increase the amount of IL-2 produced by irradiated B6 spleen cells but increased the amount of IL-2 produced in CBA anti-B6 cultures by 3·8-fold. Clone 9 cells or ASHF did not increase IL-2 production in D2-stimulated cultures. Upon stimulation with concanavalin A or antigen, clone 9 cells also produced a non-antigen-specific helper factor. This factor (IL-X) synergized with excess human recombinant IL.2 (rIL-2) in the polyclonal activation of BDF1 or D2 CTL precursors. A model that involves the participation of ASHF, clone 9 cells, IL-2 and IL-X in the induction of a cytotoxic response is proposed. [ABSTRACT FROM AUTHOR]

From our experiments and those of others in which cells were cultured at a density of 100,000 cells per well, it has been suggested that auto antibody production against mouse bromelain-treated erythrocytes (mouse brom-RBC) was independent of T cells, and further, was enhanced by the removal of T cells from responsive cell populations. Here it is shown in limiting dilution cultures that the autoimmune response is highly dependent on T cells or their products. B cells purified from the peritoneal cavities of untreated mice did not differentiate in vitro into autoantibody-secreting cells unless provided with signals from at least one of two types of accessory cells. These were plastic adherent cells and T cells, derived either from the peritoneal cavity or from established cell lines. Here it is shown that peritoneal T cells or T cells from the LBRM-33 cell line stimulated the differentiation of purified B cells in vitro in the absence of added mitogens. The accessory cell effect could be transferred in supernatants derived from T-cell cultures but not filler-cell cultures. Recombinant interleukin-2 (rIL-2) added to culture medium did not stimulate B cells directly, but could increase precursor frequencies when added to unfractionated peritoneal cell cultures, or B-cell cultures to which cells from a T-cell line had been added. From these results, it is concluded that the differentiation of precommitted peritoneal B cells in vitro into autoantibody secretors is at least partially dependent on T cells or lymphokines derived from them. Therefore, any proposed mechanisms for regulation of this autoimmune response should encompass the requirement for T cells or their products in the final differentiation stages to autoantibody secretion. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine whether the formation of hapten-specific suppressor T lymphocytes induced by the epicutaneous sensitization of UV-irradiated mice could suppress other hapten-specific immune responses in addition to contact hypersensitivity (CHS). Suppressor cells were induced by applying trinitrochlorobenzene (TNCB) to the unexposed skin of mice irradiated several days earlier with 40 kJ/m² UVB (280-320 nm) radiation. Previous work demonstrated that the spleens of such animals contain Lyt-1+, 2- T lymphocytes which prevent the induction of CHS to TNCB when transferred to normal mice, and inhibit proliferation of normal lymphocytes in vitro to TNP-modified syngeneic cells. These studies show that addition of T lymphocytes from UV-irradiated, TNCB-sensitized mice to cultures of normal lymphocytes and TNP-modified syngeneic cells inhibited the generation of TNP-specific cytotoxic T lymphocytes (CTL). The inhibition was dose-dependent and occurred only when the suppressor cells were present during the first 24 hr of culture. The suppressor cells had no effect on the activity of preformed CTL. In addition, injection of the suppressor lymphocytes into mice at the time of i.v. injection of TNP-modified sheep red blood cells (TNP-SRBC) reduced the number of direct plaque-forming cells against TNP, but had no effect on the production of antibody against SRBC. Cells that inhibited anti-TNP antibody formation were Thy-1+, Lyt-1+, 2-. These results indicate that hapten-specific suppressor cells from UV-irradiated mice prevent the activation of several different hapten-specific immunological pathways. [ABSTRACT FROM AUTHOR]

Mice of the C57BL/10 (B 10) strain are slow responders to infection with T. spiralis in terms of ability to expel worms from the intestine. Compared with rapid-responder NIH mice, infection stimulates a slower and reduced blast cell response in the draining mesenteric lymph node (MLN). Transfer of immune cells from the MLN (MLNC) does not accelerate worm expulsion from naive B 10 recipient mice, even though MLNC from this strain effectively transfer immunity to (B10 × NIH) F1 recipients. In common with other B 10 background mice C57BL/10 show an infection-dose related suppression of immunity to T. spirolis. Such suppression does not appear to determine the response to MLNC, as adoptive transfer into 810 recipients was not enhanced by reducing the level of challenge infection given, and transfer into F1 recipients was unaffected by simultaneous transfer of lymphocyte populations from donors infected at a level which would induce suppression. A hypothesis is proposed which relates slow response status to (i) the inherent capacity of the intestinal inflammatory component of worm expulsion, and (ii) the outcome of infection-dose related stimulatory and suppressive influences acting on the two interacting lymphocyte components of expulsion. The relevance of H-2-linked and non-H-2 genes to the control of the response is discussed. [ABSTRACT FROM AUTHOR]

PPD-reactive T cell clones have been used to analyse the nature of T lymphocytes that are involved in the 'heterogenization' of turnout cells. This is a phenomenon where coupling turnout cells to a strong antigen (in this case PPD) causes an enhanced immune response to tumour-specific antigens to be elicited providing that the host shows T cell immunity to the strong antigen (in this case is BCG positive). Clones of T cells with the Lyt1+ 2- phenotype which were unable to mediate delayed-type hypersensitivity but which provided efficient help to hapten-primed B cells were found to potentiate anti-turnout immunity in BCG-negative syngeneic mice when immunized with Con-A-PPD coupled, X-irradiated MC6A tumour cells. There therefore appears to be a mechanism whereby a helper T cell response to one antigen can provide help for the generation of a T cell response to a linked antigen which is analogous to the well-known phenomenon of help to hapten primed B cells. Furthermore the clones of T cells that help B cells the best are those that give maximal augmentation of T cell immunity. [ABSTRACT FROM AUTHOR]

A migration inhibition assay, using lymph node lymphocytes, has been used as an in vitro assay for cell-mediated immunity (CMI) to ovalbumin in the mesenteric lymph nodes of mice fed ovalbumin. Migration inhibition developed only if an ovalbumin feed was preceded by cyclophosphamide administration; sensitization developed within 24 hr of a single ovalbumin feed, persisted for 14 days and could be recalled on secondary oral challenge with ovalbumin. The intestinal CMI occurred in the absence of detectable systemic immunity and was found only in mice given cyclophosphamide before oral immunization. These results confirm earlier reports on induction of CMI to ovalbumin in the intestinal mucosa, and support the hypothesis that abrogation of a gut-associated suppressor system is necessary to allow induction of intestinal CMI to a dietary protein. [ABSTRACT FROM AUTHOR]

Inclusion of 14% Ficoll in the assay of rosette formation of human lymphocytes with mouse red blood cells (RBC) markedly enhances the cellular interaction. Both the strength of the rosettes (number of attached RBC) and the number of reacting lymphocytes are increased significantly, irrespective of the lymphocyte source—blood, lymph node and tonsil. In the presence of Ficoll, most of the sIg-bearing B lymphocytes [expressing receptors for Fc(IgG) and/or C3] and a significant number of the sheep RBC-rosetting T lymphocytes (particularly the nylon wool non-adherent subset from the tonsil), express receptors for the mouse erythrocyte. [ABSTRACT FROM AUTHOR]

After a primary infection with the parasitic nematode Trichinella spiralis NIH mice showed a short lived increase in cellularity of the mesenteric lymph node (MLN), which began between days 2 and 4, peaked at day 8 and had declined by day 12. The majority of cells contributing to this increase were Ig—ve and presumed to be T cells. Coincident with the increase in cell number there was an increase in lymphoblast activity, again largely in the T-cell fraction. MLN cells taken at intervals from mice during a primary infection successfully transferred immunity, i.e. accelerated worm expulsion in recipients, on days 4 and 8, but not on day 12. It was shown that the effective cells in transferring immunity were present in the T-enriched fraction. When mice were given a second infection 21 days after a primary infection the same sequence of changes was apparent in the MLN, but the time course was accelerated, i.e. peak cellularity and lymphoblast activity occurred on day 4 post challenge. Cells capable of transferring immunity were present in the MLN on days 2 and 4 post challenge but not thereafter. As in the primary infection the effective cells, and those responsible for the cellular changes in the MLN, were T cells. [ABSTRACT FROM AUTHOR]

Peripheral blood lymphocytes from baboon donors, with Schistosoma mansoni infections, were tested for in vitro activity at various times post-infection. Non-specific mitogenic responses following concanavalin A (Con A), and phytohaemagglutinin (PHA) stimulation were notably depressed between 4 and 15 weeks after a primary exposure to the parasite. Thereafter PHA and Con A reactivity returned to normal control levels. Specific cell mediated immunity was evaluated by stimulating lymphocytes in vitro with an adult worm homogenate (SWA). Significant responses to the specific were present only from 4 to 16 weeks post-infection. Thus, in the early 'acute' phase orS. mansoni infection in the baboon, approximately from 4 to 16 weeks post-infection, there occurs a notable modulation of the host's specific and non-specific cell-mediated immunity (CMl). Cells from immunosuppressed animals, with a 9-week infection, were briefly treated with trypsin and then stimulated with Con A. Such trypsinization restored the lymphocyte response back to control level indicating the possibility that a surface protein molecule on the lymphocyte was causing the reduced mitogenesis to Con A. Accordingly, sera taken from baboons over the first 30 weeks of S. mansoni infection were tested for circulating immune complexes (CIC) using 3.5% polyethylene glycol precipitation. High levels of CIC were evident from approximately 4 to 6 weeks after infection, reached maximum amounts by week 9, and thereafter declined to control levels from approximately 13 weeks onwards. Thus the appearance of CIC is largely confined to the early acute phase. Serum from 9 week infected donors caused notable suppression of the Con A response of normal cells, as did purified CIC from the same serum. From this it is proposed that CIC may play a significant role in the regulation of host cell-mediated immunity in schistosomiasis. [ABSTRACT FROM AUTHOR]

The role of mononuclear phagocyte system (MPS) in the induction of suppressor T cells which depress the delayed footpad reaction to sheep erythrocytes (SR BC) was studied in mice in which MPS was blocked or stimulated. Colloidal carbon and diethyl- stilbestrol were used for blockade and stimulation respectively. Adoptive transfer of suppressor T cells was achieved by spleen cells of mice immunized intra- peritoneally with varying doses of SRBC. In non-treated mice, 1 × 109 SRBC were required to induce suppressor T cells, while 6 × 108 could not induce the suppressor T cells. In MPS-blocked mice, however, even 6 × 108 SRBC could induce the suppressor T cells. On the other hand, 3 × 108 SRBC were required for the induction of suppressor T cells in MPS-stimulated mice. These results suggest that the activity of macrophages as scavenger cells modulates the subsequent induction of suppressor T cells after immunization with high doses of SRBC. [ABSTRACT FROM AUTHOR]

Antigen-dependent localization of 51Cr- labelled lymphocytes, and the subsequent uptake of IUdR into lymphoid organs has been studied as a function of age. Measures of cell localization indicated that while old age can alter the patterns of entry of lymphocytes into lymph nodes and spleen. these changes are variable and probably not sufficient alone to explain decreased primary antibody responses in old animals. Proliferation of cells, however, was cone sistently affected in both organs and this phenomenon is discussed in terms of abnormal T-cell function. [ABSTRACT FROM AUTHOR]

A chronic inflammation model is described which allows the study of the relationship between the level of specific cell-mediated and humoral immunity to the triggering antigen, and the presence of cells or mediators in the inflammatory exudate. In the present study special attention is paid to the participation of lymphocytes and eosinophils. Normal or FCA-pre- immunized guinea-pigs received repeated intraperitoneal injections with PPD for periods up to 21 weeks. In non-pre-immunized animals the inflammation was characterized by a strong accumulation of eosinophils, whereas only a few lymphocytes were present. In contrast, the FCA-pre-immunized guinea-pigs showed a strong lymphocytic accumulation in the absence of eosinophils. Both peritoneal inflammations were shown to remain dependent on the continuous PPD administration. Therefore, the participation of either lymphocytes or eosinophils could be directly correlated to differences in the specific immune status. Both experimental groups developed similar strong anti- PPD antibody responses as assessed by haemagglutination and passive cutaneous anaphylaxis. Only the FCA-pre-immunized guinea-pigs, however, showed strong cell-mediated immunity. The development of CMI to the continuously administered antigen appears to be a prerequisite for the accumulation of lymphocytes, while it seems to prevent antibody- mediated eosinophil accumulation. [ABSTRACT FROM AUTHOR]

The experiments reported here were designed to investigate the role of major histocompatibility antigens alone in primary allogeneic responds in vitro. Mixed lymphocyte cultures were established using small numbers of responder spleen cells and semi-allogeneic or fully allogeneic stimulator spleen cells. The cytotoxicity generated in individual cultures was then detected by a sensitive 51Cr-release assay and the frequencies of responding cytotoxic T lymphocyte precursors (CTL-P) determined by limit dilution analysis. To investigate the responses of spleen cells to major histocompatibility (H-2) antigens alone, strains of BALB/c mice congenic at the H-2 locus were used as responder and stimulator cells. The frequencies of CTL-P responding in such congenic combinations were compared with those obtained using mouse strain combinations differing at minor histocompatibility (minor-H) loci in addition to H-2. A similar fraction of spleen cells responded regardless of whether the stimulator cells differed at the H-2 locus alone or at multiple minor-H loci in addition to H-2. It was concluded that minor-H antigenic differences do not contribute significantly to allogeneic responses. [ABSTRACT FROM AUTHOR]

Mature mouse T lymphocytes, derived from long-term culture of bone marrow cells on thymus epithehal monolayers, were analysed with respect to their ability to co-operate with B cells (for antibody production) or T cells (in the generation of cytotoxic cells) when the bone marrow T precursor cells and the thymus epithelial cells differ at defined regions of the major histocompatibility complex, A pool of more mature bone marrow T-cell precursors gave rise to T cells interacting only with T/B lymphocytes sharing MHC determinants with the strain of origin of the bone marrow cells used. In contrast, a more immature bone marrow T-cell precursor pool produced T lymphocytes which had acquired MHC restriction (in terms of co-operativity with T/B cells) as defined by the MHC determinants of the thymus epithelium, and not those MHC determinants of the cultured bone marrow population. In addition, some evidence was obtained for Ir gene control (mapping in the MHC region) in the development of the repertoire of T cells involved in production of cytotoxic responses in vitro to TNP-modified self antigens. [ABSTRACT FROM AUTHOR]

Nude and normal CBA mice have been used in adoptive transfer experiments to analyse the development of immunological memory. The development of B-cell memory to xenogeneic erythrocyte antigens is to a very large degree dependent on the presence of T cells, wit h IgG memory being somewhat more dependent than IgM memory. In this system, the expression of B memory, that is the transformation of memory cells to antibody-secreting cells under the inductive influence of antigen, is largely dependent on the presence of T cells. Primed (educated) T cells can have an antigen-specific potentiating effect on unprimed B cells in the presence of antigen. [ABSTRACT FROM AUTHOR]

Using the protein A plaque assay, the number of human cells secreting immunoglobulin of various classes after pokeweed mitogen stimulation was determined. At optimal response (on day 5–7) a mean of 58,354 IgM PFC/106, 34,207 IgG PFC/106 and 10,525 IgA PFC/106 cells was found when using peripheral blood lymphocytes. In spleen cells, peak values which were slightly higher than in blood, were obtained at day 4–6. The proportions of cells secreting light chains of either type were found to be comparable to those of unstimulated cells thus supporting the notion of the polyclonality of the response. Pokeweed mitogen stimulation of peripheral blood lymphocytes was found to be totally T-cell dependent whereas the response of spleen cells was not. When assayed for antigen-specific precursor cells in cultures stimulated by mitogen, the frequency of SRBC-specific IgM producing cells was found to be 1.3/1000 cells. This frequency was regularly found to be independent of medium supplement. [ABSTRACT FROM AUTHOR]

Injection of syngeneic, but chromosomally distinguishable, lymph node or spleen cells into adult mice resulted in both T- and B-lymphocyte chimaerism. In spleen-injected mice haematopoietic chimaerism was also established. It appeared that the donor T lymphocytes were added to the host recirculating T-cell pool so that a hyperlymphoid state was produced. The percentage of donor T lymphocytes declined very slowly in normal mice, but remained stable in adult-thymectomized animals. There was no evidence of a homeostatic mechanism involving destruction of excess peripheral T lymphocytes or grossly affecting the flow of T lymphocytes from the thymus into the recirculating T-cell pool. A preliminary model of the T-lymphocyte system is proposed. [ABSTRACT FROM AUTHOR]

Lymphocytes from thirty-six normal individuals of both sexes with ages ranging from 4-89 years were tested for their cytotoxic activity against short term cultures of fibroblasts from nine foetal umbilical cords and nine adult skin samples. Wide variability in the amount of fibroblast lysis was observed. Adult male lymphocytes caused significantly higher lytic activity than lymphocytes of adult females against both types of targets. Cell- mediated target cell reduction was not confined to allogeneic target cells. There was also killing of autochthonous cultured fibroblasts, Some individuals' sera inhibited the fibroblast lytic activity of their own lymphocytes. These cell-mediated reactions are directed against unknown antigenic specifications, probably not histocompatibility antigens, and give evidence of the problem of how to measure normal controls in the microcytotoxicity test in allogeneic human testing. Both autochthonous and allogeneic target cell lysis were also observed in SLE patients. [ABSTRACT FROM AUTHOR]

The time course of the relative distribution of small lymphocytes binding 125I-labelled human thyroglobulin (HTg) in cell suspensions from the peripheral blood and various lymphoid organs was studied in guinea-pigs at progressive intervals up to 28 days after immunization with an emulsion of HTg and BCG in Freund's incomplete adjuvant (FIA). Small lymphocytes binding 125I-labelled HTg were first detected in peripheral blood, popliteal (draining) lymph node, spleen and bone marrow preparations on the 10th day, and in mesenteric (distant) lymph node and thymus preparations on the 14th day after primary immunization. In general, the percentage of these cells increased progressively thereafter until the end of the period of study. Blocking experiments with unlabelled antigens indicated that the binding of 125I-labelled HTg by small lymphocytes was specific. An anti-HTg antibody cytophilic for guinea-pig small lymphocytes was demonstrated by the passive transfer of antigen-binding capacity to lymphocytes of unimmunized animals with hyperimmune guinea-pig serum. It is proposed that, in these experiments, anti-HTg cytophilic antibody was bound first to small lymphocytes in tile tissues participating actively in the immune response (popliteal node, spleen and bone marrow) before spilling over into the general circulation to coat lymphocytes at other sites (mesenteric node and thymus). [ABSTRACT FROM AUTHOR]

Lymph node cells from preimmunized rabbits were cultured with varying concentrations of antigen in autologous serum which had been collected before immunization. [3H]Thymidine was added after 18 hours of culture and the cells were harvested at 24 or 66 hours for the determination of the radioactive labelling of acid-precipitable material. Preheating serum (56°, 20 minutes) enhanced labelling in both control and antigen-treated cultures. This 'heat effect' had an early (24 hour) non-specific component, independent of antigen concentration, and a late (66 hour) specific component which was most evident at high antigen concentrations. The conditions of preheating serum (temperature and time) required to produce the heat effect were similar to those required to remove haemolytic activity against rat erythrocytes. However, at certain temperatures and times there were discrepancies. These discrepancies, and data from experiments in which preheated and unheated sera were mixed in varying proportions, or interchanged in different sequences, were explicable on the basis of (i) a requirement for complement in stoichiometric quantities dependent on the number of cells being inhibited, (ii) the involvement of the majority of the cultured cells in the early non-specific component of the heat effect, but only cells capable of proliferating in response to added antigen in the late specific component, (iii) the secretion of complement by cultured cells. Preheating serum (66&deg:, 20 minutes) depressed labelling in control and antigentreated cultures and reduced agglutinating activity against both autologous and heterologous erythrocytes. The results are discussed in relationship to models which require that the size of a specific lymphocyte clone be positively or negatively regulated by the concentration of antigen specific for that clone. With increasing antigen concentration three effects on cells bearing specific receptor sites are distinguished. (i) Cell stimulation under conditions of antigen concentration and cell receptor specificity such that only a few antigen molecules can bind to cells. (ii) Complement-dependent inhibition under conditions such that more antigen molecules can bind to cells. (iii) Complement-independent inhibition under conditions, possibly unphysiological, such that very large quantities of antigen molecules can bind to cells. [ABSTRACT FROM AUTHOR]

The chemoattractant effect of soluble protein antigens for B cells from immunized mice was examined. Mice were immunized either via the footpad with ovalbumin (OVA) in complete Freund's adjuvant (CFA) or with CFA alone; or intraperitoneally with OVA incorporated in immune-stimulating complexes (OVA-ISCOM) or with saline. After 8-14 days B cells were purified from the spleens or the draining popliteal nodes and tested in vitro for locomotor responses to antigen using polarization (shape-change) and filter assays. Cells obtained by both routes of immunization, but not cells from control mice, gave locomotor responses to OVA. Responses were seen in B cells directly after preparation (5-8% of cells responding) but were enhanced if the cells were cultured overnight in the presence of interleukin-4 (IL-4) before testing (10-12% of cells responding). Checkerboard filter assays suggested that the response to OVA was chemotactic. The response was antigen specific since cells from OVA-immunized mice did not respond to bovine serum albumin (BSA), and cells from BSA-immunized mice responded to BSA but not to OVA. The response to OVA was inhibited by preincubation of OVA with anti-OVA but not with anti-BSA. Many of the cells that polarized in response to antigen were larger than any B cells found in control populations suggesting that the responsive cells are those that had been stimulated to enter cell cycle following immunization. [ABSTRACT FROM AUTHOR]

The mouse Nrampl (Bcg) gene on chromosome 1 exerts pleiotropk effects on macrophage function. The gene is known to affect presentation of mycobacteria, and other antigens in vitro, so that macrophages carrying the resistant Bcg allele better support the proliferation of antigen-specific T cells compared with macrophages of the sensitive phenotype. To determine whether the Bcg allele could affect in vivo the antibody response to antigens not related to mycobacterial infections, we tested the primary and secondary responses to sheep red blood cells (SRBC) and glycosylated bovine insulin (G-insulin) in two pairs of Bcg congenic strains: BALB/c (Bcgs) versus BALB/c.CD2 (Bcgr), and B10.A (Bcgs) versus B10Ar (Bcgr), and in C57BL/10ScSn (B10; Bcgs) and A/J (Bcgr) mict. Furthermore, the antigen-specific proliferative responses of T cells primed in vivo by protein antigens were also tested in Bcg congenic mice. We found no significant difference in vim antibody response either to SRBC or G-insulin between the Bcgr and Bcgs strains. The magnitude of in vitro antigen-specific proliferation of lymph node cells sensitized in vivo by hen egg lysozyme (HEL) or chicken ovalbumin (OVA) was also similar in Bcgs and Bcgr congenic mice. However, we have documented a higher antigen-presenting capacity of Bcgr macrophages in vitro antigen-specific proliferation to OVA. Since the macrophages are the only cells in which the Nrampl gene is expressed, we suggest that the activity of other types of antigen-presenting cells masks the effect of the Bcgr allele on antigen-presentation in vivo. [ABSTRACT FROM AUTHOR]

In this study, we examined the ability of varying populations of donor cells from B6 mice to induce hyporesponsiveness in T lymphocytes from C3H mice in vitro and in vivo. Small, resting B lymphocytes were inefficient stimulators of T-lymphocyte proliferation compared to splenic mononuclear cells (SMNC) and lipopolysaccharide (LPS)-induced B-cell blasts in vitro (P < 0.05). Pretreatment of SMNC with anti-B7-1 or anti-intracellular adhesion molecule-1 (ICAM-1) monoclonal antibodies (mAb) similarly resulted in inefficient stimulation of T-cell proliferation in vitro (P < 0.05). However, in vivo, only intrahepatic, but not intravenous, injection of donor cells into C3H mice resulted in decreased T-lymphocyte proliferation in response to restimulation by alloantigen. This effect was most pronounced following intrahepatic injection of resting B lymphocytes or SMNC pretreated with anti-ICAM-1 mAb compared to uninjected or intravenously injected mice (P < 0.05). The hyporesponsiveness was associated with an increased production of interleukin-4 (IL-4) by the responder T lymphocytes and correlated with enhanced skin allograft survival. These data demonstrate that intrahepatic injection of donor-derived cells induces T-lymphocyte hyporesponsiveness. The mechanism appears to be modulated by an ICAM-1-mediated signal resulting in expansion of an IL-4-producing T-lymphocyte population. [ABSTRACT FROM AUTHOR]

In this study the involvement of peripheral γδ T cells, prepared by flow cytometry, in the immune response of cattle to primary infection with Trypanosoma congolense was assessed. Negligible in vitro proliferative responses were observed in γδ T cells isolated from trypanosusceptible Boran (Bos indicus) cattle at all stages examined post-infection when stimulated in vitro with parasite antigens. In contrast, both CD8+ T cells and γδ T cells from trypanotolerant N'Dama (Bos taurus) cattle proliferated markedly when stimulated in vitro with a complex of invariant trypanosome antigens with MW between 100 000 and 140 000 (100 000 MW complex). Neither species of cattle exhibited significant T-cell recognition of trypanosome variable surface glycoprotein (VSG). To study further the functional and phenotypic characteristics of the γδ T-cell response, four T-cell lines were established from infected N'Dama cattle. These cell lines were comprised of up to 96% γδ (WC1+) T cells, the remainder being CD8+ T cells. Two of these γδ T-cell lines exhibited 100 000 MW complex antigen specificity which was not major histocompatibility complex (MHC) restricted in one line. [ABSTRACT FROM AUTHOR]

Mice injected at birth with semi-allogeneic lymphoid cells develop a lupus-like autoimmune syndrome in which donor B cells are polyclonally activated by host alloreactive CD4+ T cells, producing autoantibodies and immune complex-mediated glomerulonephritis. It has been demonstrated that the recognition of major bistocompatibility complex (MHC) class II alloantigens triggers the development of a complete disease. But differences in either MHC class I molecules or Mls-l antigens are not sufficient to induce production of autoantibodies. Here we have investigated whether differences in other non-MHC alloantigens could induce a similar autoimmune disease and whether the maternal environment could modulate the T-B allogeneic co-operation in this model. For this purpose (BALB/c × BC20)F1 hybrid females were backcrossed with BC20 males. R2 mice obtained in this backcross were neonatally injected with 108 (C57BL/6 × BALB.Igb')F1 spleen cells and the tolerance against maternal derived BALB/c alloantigens as well as the development of autoimmune manifestations were subsequently evaluated. In contrast to R2 mice injected at birth with (C578L16 &times BALB.Igb')F1 cells, control R2 mice rejected skin grafts from BALB/c mice and B cells from (C57BL/6 × BALB.Igb')F1 mice, independently of their H-2 haplotype (H-2b/d or H-2b/b). Nevertheless, after neonatal injection of (C57BL/6 × BALB.Igb)F1 cells, none of 19 H-2b/d R2 injected mice presented autoimmune manifestations, in contrast with the typical autoimmune disease observed in all neonatally injected H-2b/b R2 mice (26 mice). These results support that the development of autoimmunity in this model depends exclusively upon differences in MHC class II alloantigens and that the relationship between mother and fetus, through the pregnancy or the breast suckling, is not sufficient to inhibit cytolytic and allo-helper responses against non-inherited maternal-derived alloantigens. [ABSTRACT FROM AUTHOR]

BoCD4+T-cell clones specific for a peptide derived from foot-and-month disease virus envelope protein, VP1 (FMDV15) were generated from two responder cattle. One animal was a high and the other was an intermediate responder in terms of both T-cell and antibody responses. However both animals had identical major histocompatibility complex (MHC) class II DR-like types (DRBF3,6) according to a one-dimensional isoelectric focusing method which distinguishes DR-like alleles. In contrast, mixed lymphocyte reaction (MLR) responses indicated that they shared only one haplotype (DRBF3) and anti-DRBF6 alloclones also differentiated between the animals. This suggested that the animals differed at a non-DR-like locus. Restriction patterns of FMDV-specific clones derived from these animals indicated that FMDV15 was presented by the non-DR-like class II molecules associated with DRBF6. Only one clone, derived from the high responder animal, was restricted to DRBF3. Thus products from the non-DR-like locus (probably DQ-like) are functionally important for presentation of FMDV peptides. Furthermore the allelic differences detected by the alloclones are also critical for peptide binding. The majority of clones from the high responder animal recognized an immunodominant region containing a Rothbard epitope whereas none of the clones from the intermediate responder did so. This suggests that the region recognized by T cells, which is dependent upon MHC type, influences the B-cell response and thus the degree of protection obtained. This has major implications for rational vaccine design involving T- and B-cell epitopes. [ABSTRACT FROM AUTHOR]

This study analysed the effect of Schistosoma japonicum egg antigens (SEA) on the activation of lymphocytes from naive mice. T cells were found to be unaffected by SEA. B cells, however, were activated by SEA without participation of adherent cells such as macrophages. B-cell activating factor(s) in SEA were distributed into a fraction of Mr 120,000 and a fraction of Mr 650,000 by gel filtration. However, a fraction of Mr 120,000 demonstrated thc presence of a limited number of components by polyacrylamide gel electrophoresis (PAGE) under non-denaturing conditions. These activating factor(s) were destroyed by peroxidase oxidation, heat treatment, chymotrypsin and trypsin digestion. These results indicate that the B-cell activating factor(s) in SEA contain both carbohydrate and protein. IgM antibodies were detected in the culture supernatant of SEA-activated B cells after 48 hr in culture, but IgG antibodies were undetected in culture. These antibodies did not react with SEA but reacted with sheep, horse, mouse red blood cells, carbonic anhydrase and autoantigens in myelinated nerve fibres of cerebrum as well as luminal surface and parietal cells of the stomach of naive mice. Thus our data demonstrated that SEA directly stimulates naive B cells to produce antibodies against heterophile and autologous antigens. [ABSTRACT FROM AUTHOR]

Short-term (3 hr) incubation of whole blood with human recombinant cytokines induced rapid changes in the expression of monocyte but not of lymphocyte surface molecules. The percentage of monocytes bearing CD11b molecules was enhanced by tumour necrosis factor-beta (TNF-α), whilst that of CD11c was increased by both TNF-α and TNF-β. The mean fluorescence intensity (MFI) of monocyte CD11a was enhanced by interleukin-2 (IL-2), TNF-α and TNF-β, and that of CD11b. CD11c and CD18 was increased by IL-2, IL-4, TNF-α and TNF-β. The proportion of monocytes expressing HLA-DR antigens was not modified by the cytokines investigated, but its MFI was increased by IL-2, IL-4, TNF-α and TNF-β. In contrast, the percentage of monocytes bearing complement receptor 1 (CD35) was enhanced by IL-2, TNF-α and TNF-β but the MFI of this molecule was not modified by these cytokines. The highest up-regulation of CD18, HLA-DR and CD35 was observed with 100 U/ml of either IL-2. IL-4, TNF-α or TNF-β. Decreasing the concentration of all four cytokines from 100 to 10 and 1 U/ml diminished the levels of expression of all molecules, with the exception of CD35, which reached its maximum upon incubation with I U/ml of TNF-α. IL-1β, IL-6 or interferon-gamma (IFN-γ) did not modify the expression of any of the above monocyte surface determinants. Moreover, none of the lymphocyte surface molecules investigated was modified by 3-hr incubation of blood with cytokines. The demonstration that cytokines selectively and rapidly up-regulate integrins, complement receptor 1 and HLA-DR molecules, on monocytes but not on lymphocytes, suggests that similar mechanisms of mononuclear cell activation by cytokines may control the development and duration of the inflammatory process. [ABSTRACT FROM AUTHOR]

During primary tsetse-transmitted challenge of Boran (Bos indicus) cattle with Trypanosoma congolense ILNat 3.1, a transient parasite antigen-specific T-cell proliferative response was observed in peripheral blood mononuclear cells and splenic mononuclear cells stimulated in vitro. A response was also observed with cells of N'Dama (Bos taurus) cattle, but in this case higher stimulation indices were observed and the response was maintained until the termination of the experiment at 40 days post-infection (p.i.). The highest parasite antigen-specific proliferative responses were observed at 20 days post-infection. At this time N'Dama cattle not only responded to the antigens derived from the infecting clone (ILNat 3.1), but also to antigens from a clone of a different serodeme (ILNaR 2), whereas Boran cattle only recognized antigens from the infecting clone of parasites. To determine the molecular mass of the antigenic trypanosome proteins, whole trypanosome lysates made from T. congolense ILNat 3.1 were fractionated by SDS-PAGE and transferred onto nitrocellulose membranes. The major protein bands were isolated and used directly in T-cell proliferation assays, In this instance, no differences in the antigen recognition profiles of Boran and N'Dama cattle were observed. The variable surface glycoprotein did not induce T-cell proliferation in infected cattle despite the presence of serum antibodies to this variable antigenic type. [ABSTRACT FROM AUTHOR]

Guinea-pigs were immunized with emulsions of protein antigens in Freund's complete adjuvant. Draining lymph node cells were cultured for 20 hours together with the immunizing antigen; after harvesting, the culture supernatants were added to fresh lymphocytes from allogeneic or autochthonous guinea-pigs, and these 'recipient' cells were maintained in culture for 3 days. Uptake of [³H]thymidine was measured during the last 18 hours of culture, and revealed that the lymphocyte culture supernatants induced greater thymidine uptake by the 'recipient' lymphocytes than could be expected from the amount of antigen present in the cultures. The soluble factor which mediates this effect was termed 'mitogenic factor'. Analysis of this phenomenon revealed that the mitogenic factor was only generated by interaction between sensitized lymphocytes and the specific antigen used for sensitization; but that once induced, the soluble mitogenic factor was equally active on non-sensitized and sensitized lymphocytes. It is suggested that the mitogenic factor contributes towards the expression of cell-mediated immunity and that it may participate in regulation of the immunological response. [ABSTRACT FROM AUTHOR]

This investigation was conducted in two parts: first establishing separatory and cultural procedures for bovine lymphocytes, and then studying the in vitro response of these cells following stimulation with phytohaemagglutinin (PHA) and cellular constituents of Streptococcus agalactiae (St. ag.). Peripheral lymphocytes from normal animals, those with chronic St. ag. udder infections, and animals hyperimmunized with cellular constituents of St. ag. were studied. The bovine lymphocyte responded to PHA with blastogenic changes similar to those of the human lymphocyte. No changes in cellular morphology or cytochemistry were detected following in vitro stimulation with cell antigens of St. ag. Lymphocytes from hyperimmunized animals were shown to be capable of in vitro transformation in response to a different antigenic stimulation. Several explanations for this immunological inertia are presented.

An increased number of lymphocytes with active nucleoli was found in the peripheral blood of most patients suffering from connective tissue diseases associated with autoimmunity. [ABSTRACT FROM AUTHOR]

Monoclonal antibodies have been produced that bind to four different antigens expressed on the surface of ovine lymphocytes as well as to a variety of other ovine cell types. These antigens have been characterized with respect to their tissue distribution and immunochemistry. The timing of appearance of these antigens within the ovine embryo is reported. [ABSTRACT FROM AUTHOR]