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Summary Major histocompatibility complex (MHC) class I-specific inhibitory receptors are expressed not only on natural killer (NK) cells but also on some subsets of T cells. We here show Ly49 expression on γ/δ T cells in the thymus and liver of β2-microglobulin-deficient (β2m-/-) and C57BL/6 (β2m+/+) mice. Ly49C/I or Ly49A receptor was expressed on NK1.1+γ/δ T cells but not on NK1.1-γ/δ T cells. The numbers of NK1.1+γ/δ T cells were significantly smaller in β2m+/+ mice than in β2m-/- mice with the same H-2b genetic background. Among NK1.1+γ/δ T cells, the proportions of Ly49C/I+ cells but not of Ly49A+ cells, were decreased in β2m+/+ mice, suggesting that cognate interaction between Ly49C/I and H-2Kb is involved in the reduction of the number of Ly49C/I+ γ/δ T cells in β2m+/+ mice. The frequency of Ly49C/I+ cells in NK1.1+γ/δ T cells was lower in both lethally irradiated β2m+/+ mice transplanted with bone marrow (BM) from β2m-/- mice and lethally irradiated β2m-/- mice transplanted with BM from β2m+/+ mice than those in adult thymectomized BM-transplanted chimera mice. These results suggest that reduction of Ly49C/I+ NK1.1+γ/δ T cells in β2m+/+ mice is at least partly due to the down-modulation by MHC class I molecules on BM-derived haematopoietic cells or radioresistant cells in the thymus. [ABSTRACT FROM AUTHOR]

Summary Cytomegalovirus (CMV) causes severe opportunistic infection in immunocompromised hosts. The importance of conventional αβ T cells in protection against CMV infection has been well documented. However, the role of the second T‐cell population (which express the γδ T‐cell receptor) in CMV infection is not known. In the present study, we analysed the function and protective role of γδ T cells in a murine cytomegalovirus (MCMV) infection model. After intraperitoneal infection with MCMV, the number of γδ T cells increased in the liver and peritoneal cavity from day 3, and reached a peak on day 5. The γδ T cells showed an activated T‐cell phenotype and predominantly expressed Vγ1, which is known to be expressed by heat‐shock protein 65 (hsp 65)‐specific γδ T cells. Analysis of cytokine expression demonstrated that the MCMV‐induced γδ T cells expressed interferon‐γ (IFN‐γ) and tumour necrosis factor‐α (TNF‐α) but not interleukin‐4 (IL‐4), implying their participation in the cell‐mediated immune response against MCMV. Depletion of γδ T cells by anti‐T‐cell receptor (TCR) γδ monoclonal antibody (mAb) treatment resulted in significant increase of virus titre and decrease of IFN‐γ in the liver on day 3 after MCMV infection, which further supports the importance of γδ T cells in early protection against infection. Finally, the MCMV‐induced γδ T cells produced IFN‐γ in vitro in response to hsp 65. Our results suggest that γδ T cells participate in early protection against MCMV infection through recognition of hsp 65 and production of IFN‐γ. [ABSTRACT FROM AUTHOR]

Recombinant human granulocyte colony-stimulating factor (rh G-CSF) enhanced resistance of mice against Listeria monocytogenes (LM) as determined by survival and bacterial growth. Mice pretreated with rh G-CSF twice daily for 5 days survived better than untreated animals to the challenge with LM. Number of bacteria in peritoneal cavity (PC) and spleen was lower in treated mice than that in the control group. RhG-CSF increased mainly polymorphonuclear cells (PMN) in blood and spleen. After LM inoculation, a larger number of PMN and monocyte-macrophages accumulated in PC and spleen of tested mice. In addition, PMN primed in vivo with rh G-CSF released more superoxide anions when stimulated with phorbol myristate acetate. The inhibition of bacterial growth in PC and spleen could be ascribed to the accumulation of phagocytic cells at the infection sites and the increased oxidative metabolism. The results provided further evidence of the important contribution of G-CSF and neutrophils, as target cells, to the host defence against the intracellular bacteria. [ABSTRACT FROM AUTHOR]

In flow microfluorometry analysis of thymus and lymph node cells of C57BL/6(I-E-,Mlsb) mice rendered neonatally tolerant to (C57BL/6 × AKR/J)F1 (I-E+,Mlsb/a) lymphoid cells, both CD4+ and CD8+ cells showed a striking reduction in the number of Vβ6+ cells capable of recognizing Mlsa in the context of major histocompatibility complex (MHC) class II molecules, indicating that clonal deletion of Vβ6+ cells by Mlsa antigen occurs just at a stage of immature Vβ6lowCD4+CD8+thymocytes. On the other hand, the number of Vβ11+ cells capable of recognizing I-E was markedly reduced in CD4+ cells, but CD8+ cells showed only partial (20%) reduction of such a population. The clonal deletion of Vβ11+ cells by I-E may begin at the transitional stage from Vβ11lowCD4+CD8+ to Vβ11highCD4+CD8- single-position cells, and Vβ11lowCD4+CD8+ cells differentiating to Vβ11highCD4-CD8+ cells seem to be resistant to clonal deletion. Vβ11+ T cells are also stimulated by staphylococcal enterotoxin A (SEA) irrespective of expression of CD4 or CD8. Nearly all of both Vβ11+CD4+ and Vβ11+CD8+ lymph node T cells were deleted by the injection of SEA every other day from birth. In their thymi, both Vβ11+CD4+CD8- and Vβ11+CD4 CD8+ single-positive thymocytes were deleted, and the proportion of Vβ11low thymocytes was lower than that of normal mice. The clonal deletion of Vβ11+ T cells by SEA injection occurs at a stage of immature Vβ11lowCD4+CD8+ double-positive thymocytes, resulting in deletion of both Vβ11+CD4+ and Vβ11+CD8+ T cells. [ABSTRACT FROM AUTHOR]

We have previously reported that T-cell receptor (TcR) γδ-bearing T cells precede TcR αβ-bearing T cells in appearance in the thymus after whole-body irradiation. In the present study, the kinetics of appearance of intestinal intra-epithelial lymphocytes (IEL) was examined in mice after whole-body irradiation with a lethal dose of 9.5 Gy or with a sublethal dose of 6 Gy. The number of CD3+ IEL decreased to the lowest value 4 days after irradiation with 9.5 Gy, and thereafter increased to half as many as the normal level by day 7. Thy-1+TcRαβ- IEL and Thy-TcRβ IEL recovered considerably by day 7 after the irradiation, whereas Thy-1+TcRαβ+ IEL and Thy-1+TcRαβ+ IEL hardly recovered at this stage. All mice died within 12 days after irradiation with a lethal dose of 9.5 Gy. On the other hand, when irradiation dose was decreased to 6 Gy, all mice survived beyond 40 days after irradiation. The number of CD3+ IEL recovered to the normal level by 10 days after irradiation with 6 Gy. Consistently with the results in mice irradiated with a lethal dose, the first cells to increase in IEL of mice irradiated with a sublethal dose were TcRγδ+ IEL expressing Thy-1 antigen. The number of Thy-1+TcRγδ+ IEL increased to approximately two-fold as many as that in normal mice by day 10, while TcRαβ+ IEL began to increase in number from day 20 after irradiation and recovered to the normal level by day 40 after irradiation. Thus, sequential appearance of TcRγδ+ and TcRαβ+ IEL was evident after irradiation, similar to that seen in the thymus after irradiation. The IEL on day 10 after sublethal irradiation, which is composed mainly of Thy-1+TcRγδ+ IEL, exhibited a strong cytolytic activity against P815 in the presence of anti-CD3 mAb, suggesting that the early appearing Thy-1+TcRγδ+ IEL may play important roles in epithelial immunity at an early stage after irradiation. [ABSTRACT FROM AUTHOR]

Murine thymocytes are divided into four major populations on the basis of expression of CD4 and CD8 antigens. The bulk of evidence favours the view that CD4-CD8- cells can develop into CD4-CD8+ and CD4+CD8- cells via the CD4+CD8+ stage in the thymus. However, CD4-CD8+ and CD4+CD8- thymocyte subsets contain not only CD3+ mature cells but also CD3- immature cells, which seem to be intermediate cells between CD4-CD8- and CD4+CD8+ cells. Here we demonstrate mouse strain differences in the proportion of immature single-positive thymocyte subsets in thymus at the steady or developing state. In C3H mice, immature CD4+ CD8- is dominant in proportion over CD4-CD8+ in foetal thymus and in donor-derived thymocytes at an early stage of bone marrow transplantation. On the other hand, immature CD4 CD8+ is dominant over CD4+CD8- during T-cell development in the case of B10.BR mice. An intermediate pattern was shown in the case of Fi mice. Both of these immature single-positive subsets gave rise to doublepositive cells after 24 hr culture. These results suggest that there exist two distinct differential pathways; one is from CD4- CD8- cells to CD4+ CD8+ cells via CD4-CD8+ cells, and another is via CD4+CD8- cells, and that an application of the 'CD8 pathway' or 'CD4 pathway' seems to be genetically destined by BM-derived cells but not by thymic stromal cells. [ABSTRACT FROM AUTHOR]

In order to search for a possible role of abnormally proliferating T cells in developing autoimmune disease in lpr mice, and to define the difference of the T ceils among various lpr-congeneic mice with different clinicopathological findings, the T-cell receptor (TcR) Vβ gene expression in the enlarged lymph nodes (LN) of C3H/HeJ-lpr/lpr (C3H-lpr), C57BL/6-1pr/lpr (B6-lpr) and MRL/Mp-lpr/lpr (MRL-lpr) mice was analysed. A RNA blot analysis using several Vβ-specific probes showed that the Vβ3 gene, whose products are important for recognizing Mlsb/a, was used in B6-lpr and MRL-lpr with the Mlsb/b but not in C3H-lpr with the Mlsb/a. The Vβ5 gene, which is selectively related to I-E molecules, was predominantly used in B6-lpr(I-E-) but not in C3H-lpr(I-E+) nor MRL-lpr(I-E+). Similarly, the V12 gene was also expressed in B6-lpr but not in C3H-lpr. To compare in detail the Vβ repertoire among lpr mice with different major histocompatibility complex (MHC) backgrounds, the Vβ gene sequences in the cDNA libraries from LN cells of C3H-lpr were analysed, following the recent investigation of B6-lpr mice (Ohga et al., 1989). Eleven β-chain cDNA out of 32 β cDNA in B6-lpr and 24 β-chain cDNA out of 55 β cDNA in C3H-lpr were found to contain sequences with open reading frames that potentially encode functional TcR β-chain. The fequencies of the messages in the cDNA libraries from these mice were consistent with the RNA blot analysis using Vβ3- and Vβ5-specific probes. It was notable that 36% of the functional β-chain mRNA in B6-lpr and 50% of the β mRNA in C3H-lpr expressed the Vβ8 gene family. When the TcR Vβ gene expression was compared between the LN cells in C3H-lpr, B6-lpr and MRL-lpr, as reported by Singer et al. (1986), the usage of Vβ genes other than the Vβ8 gene family in B6-lpr (H-2b) LN cells differed significantly from those in C3H-lpr (H-2k) and MRL-lpr(H-2k). The results presented here indicate that the usage of Vβ genes is heavily influenced by the genetic background of lpr mice, similar to normal mice, but with preferential usage of the Vβ8 gene family as a common structural feature in lpr gene-induced cell populations. [ABSTRACT FROM AUTHOR]

It has been reported previously that environmental antigens such as intestinal microflora play an important role in an age-associated increase in number of T-cell receptor γ/δ-bearing T cells. To extend the scope of this finding, this study examined the influences of local inflammation on the accumulation and/or proliferation of γ/δ T cells in athymic nude mice injected subcutaneously with complete Freund's adjuvants (CFA). The inguinal lymph nodes (ILN) in nude mice injected with CFA in their hind footpads 7 days previously contained an increased number of CD3+CD4-CD8 cells. Increased levels of proliferative responses against syngeneic stimulator cells were noted in the LN cells of CFA-injected nude mice in association with increases in expression of γ-and δ-chain gene messages. Furthermore, the LN cells showed an early proliferative response to purified protein derivative (PPD) from Mycobacterium boris. These results suggest that local inflammation by CFA may induce functional γ/δ T cells in nude mice, which may proliferate rapidly at the inflamed sites and represent a first line of defence in such animals against the invasion of various pathogens. [ABSTRACT FROM AUTHOR]

Clonal deletion oft cells capable of recognizing both host-type M1s and donor-type M1s occurred in the peripheral mature T-cell pool in radiation bone marrow chimeras of two H-2-compatible M1s disparate strain combinations of AKR/J(H-2k,Thy-1.1,Mls-1a) and C3H/He(H-2k,Thy-1.2,M1s-1b). In order to determine further the stage at which the clonal deletion occurs in thymus, we examined the kinetics of thymocytes bearing Vβ6 capable of recognizing M1s-1a in both C3H/He→AKR/J and AKR/J→C3H/He chimeras. An almost complete replacement from host-derived cells to donorderived cells occurred by Day 21 after reconstitution in both chimeras. At this stage, CD4+CD8+ double-positive thymocytes contained an appreciable number of cells that expressed Vβ6 on their surface, albeit at Iow intensity, whereas CD4 or CD8 single-positive thymocytes which expressed a high density of Vβ6 were virtually abolished in both C3H→AKR and AKR→C3H chimeras on Day 21. These results suggest that clonal deletion of self-M1s-reactive T cells begins at an early stage when the thymocytes interact with the early appearing donor-derived haematopoietic cells and relatively radio-resistant host-derived cells in thymus of radiation bone marrow chimeras. [ABSTRACT FROM AUTHOR]

To search the abnormality in prethymic T-cell precursors in lpr/lpr(lpr) mice, rearrangement and expression of T-cell receptor (TcR) genes were investigated in long-term cultured bone marrow (LTBM) cells of lpr mice, in which the developmental steps of T-cell purcursors may be better synchronized than those in bone marrow (SM) cells. Neither rearrangment nor expression of TCR γ and δ genes were detected in the LTBM cells from +/+ control mice, whereas some γ gene rearrangements were detected in those derived from lpr mice, irrespective of the genetic background. When BM cells or LTSM cells from lpr mice were transplanted into supralethally irradiated +/+ mice, the lpr-derived BM cells appeared earlier in the thymus of the recipient mice than +/+-derived BM cells and the recipients suffered from lethal wasting syndrome. In addition, the lpr-derived SM cells showed higher activity in colony-forming unit spleen (CFUs) than the +/+-derived SM cells. These results suggest that the T-cell progenitors in the SM of lpr mice may be different not only in quantity but also in quality from those of +/+ mice. [ABSTRACT FROM AUTHOR]

We have previously shown that extrathymic rearrangements of T-cell receptor (TcR) γ and δ chain genes occur in the peripheral lymphoid tissues of athymic nude mice. To further determine where the TcR gene rearrangements occur in nude mice, we investigated the rearrangement and expression of the TcR genes in the long-term cultured bone marrow (LTBM) cells which were homogenous in developments without mature T cells as assessed by FACS analysis. The LTBM derived from euthymic mice contained IcR γ and δ chain genes in germline configuration, while gene rearrangements of both locus were detected in the LTBM cells from nude mice. These results suggested that γ and δ gene rearrangements do occur in the bone marrow cells of nude mice and that the T-call precursors in bone marrow may be increased in frequency in such animals. [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]

Delayed footpad reactions and acquired cellular resistance to Listeria monocytogenes were studied in mice whose mononuclear phagocyte system (MPS) had been blocked or stimulated. Colloidal carbon was used for the blockade of MPS and Corynebacterium parrum used for the stimulation. Strong delayed footpad reactions. On the other hand, the i.v. rejection of 3 × 101; listeria induced an appreciable level mice, while in MPS-stimulated mice, i.v. injection with even 4 × 103; listeria could not induce such strong delayed footpad reaction. On the other hand, the i.v. injection of 3 × 10¹ listeria induced an appreciable level of delayed footpad reaction only in MPS-blocked mice. Acquired cellular resistance was depressed by MPS stimulation, whereas it was augmented by MPS blockade. These results suggested that non-specific activity of MPS modulates subsequent immune responses after inoculation of listeria. [ABSTRACT FROM AUTHOR]

The delayed footpad reaction to sheep erythrocytes (SRBC) was studied in mice whose mononuclear phagocyte system (MPS) was blocked or stimulated. Colloidal carbon or carrageenan was used for the blockade of MPS and Corynebacterium parvurn or diethylstilbestrol used for the stimulation. The optimal dose of SRBC for the induction of the delayed footpad reaction was lower in MPS-blocked mice than in non-treated mice, whereas a high dose of SRBC was required for the induction of the strongest delayed footpad reaction in MPS-stimulated mice. These results suggest that non-specific phagocytic function of MPS modulates subsequent immune responses after administration of antigens. [ABSTRACT FROM AUTHOR]

Neonatally thymectomized (NTx) mice, whose ability to mount antigen-specific cell-mediated immunity is reported to be generally defective, were found to be capable of mounting a normal level of acquired cellular resistance (ACR) and delayed footpad reaction (DFR) to Listeria monocytogenes. The present study was done in order to determine the functional differences of T cells contributing to the protection against L. monocytogenes between NTx and sham-operated mice. In mice immunized with viable L. monocytogenes, the absolute number of splenic T cells was significantly lower in NTx mice compared with sham-operated mice. When the ability of immune T cells to transfer ACR and DFR was examined by passive transfer, lymphocytes from immune NTx mice conferred a higher level of ACR and DFR on naive recipient mice, despite the marked difference in total number of T cells compared with immune Sham mice. Antigen-specific proliferation and interleukin-2 (IL-2) production by splenic T cells from immune NTx mice were significantly lower than in those from immune Sham mice. The proliferative response of T cells to exogenous IL-2 was also lower in NTx group. These results suggest that the requirement for the IL-2-driven T-cell proliferation system is basically low in the generation of effector T cells specific for L. monocytogenes. [ABSTRACT FROM AUTHOR]

We examined the host defence mechanism against infection with Listeria monocytogenes, a facultative intracellular bacterium, in mice with murine acquired immunodeficiency syndrome (MAIDS) caused by LP-BM5 murine leukaemia virus (MuLv) infection. Although LP-BM5 MuLV infection in C57BL/6 mice leads to a stage of immunodeficiency characterized by severe compromise of cell-mediated immunity, the mice with established MAIDS infected with LP-BM5 8 weeks previously, showed resistance to an intraperttoneal infection with Listeria monocytogenes. These MAIDS mice also showed resistance to a lethal dose of secondary listerial challenge, while the delayed-type hypersensitivity response to heat-killed Listeria (HKL) was severely impaired in MAIDS mice. The resistance of MAIDS mice to listerial infection was mediated by CD4+ αβ T cells but neither by γδ T cells nor natural killer (NK) cells. Interferon-γ (IFN-γ) and interleukin-10 (IL-10) were produced by CD4+ T ceils from Listeria-infected MAIDS mice in response tO the in vitro stimulation with HKL, whereas IFN-γ but not IL-10 were produced by those from Listeria-infected control mice. These results suggest that T-helper 0 (Th0)-like immune responses of CD4+ T cells occur and participate in host defence mechanisms against listerial infection in MAIDS mice. [ABSTRACT FROM AUTHOR]

We have previously reported that heat-shock protein (hsp) 60-reactive T-cell receptor (TCR)γδ+ T cells appear in the peritoneal cavity during the early stage of infection with Listeria monocytogenes in mice. In this study, we examined the kinetics of TCRγδ+ T cells during listeriosis in F344 ruts by flow cytometry using a V65 monoclonal antibody (mAb) directed to a constant determinant of rat TCRγδ chains. TCRγδ+ T cells significantly increased in the peritoneal cavity on day 6 and then decreased by day 10 after infection, in parallel with the kinetics of hsp 60 expression in the peritoneal macrophages during listeriosis in F344 rats. Most of the early appearing TCRγδ+ T cells were of the CD4- CD8αβ+ CD5+ lymphocyte function-associated antigen (LFA)-1αhigh CD45RC- interleukin-2 receptor (IL-2R) α- phenotype, although a significant fraction of the TCRγδ+ T cells expressed CD8σ only. The increase in TCRγδ+ T cells during listeriosis was prominent in F1 (F344 × Lewis) rats but only marginal in Lewis rats, which was correlated with the expression level of hsp 60 in the peritoneal macrophages. The peritoneal TCRγδ+ T cells in naive F344 rats appeared to proliferate significantly in response to recombinant hsp 60 (rhsp 60) derived from Mycobacterium bovis bacillus Calmette-Guérin (BCG). These results imply that the early appearance of hsp 60-reactive TCRγδ+ T cells during listerial infection can be generalized across species. [ABSTRACT FROM AUTHOR]

Conversion of Salmonella typhimurium to L-forms, both in vitro and in vivo, resulted in the expression of proteins cross-reacting to the mycobacterial 65000 MW heat-shock protein (hsp). Immunization of C3H/HeJ mice with a protective dose of stable L-form S. typhimurium induced γδ T cells in the liver, in accordance with the multiplication of L-form Salmonella in Kupffer cells. The number of γδ T cells decreased after the intracellular growth of L-form Salmonella plateaued. Persistance of the L-forms in Kupffer cells, however, allowed hepatic γδ T cells to increase within 48 hr of infection with virulent S. typhimurium. Thus, the intrahepatic colonization of L-form Salmonella seems to keep γδ T cells on standby, but the emergence of these T cells does not correlate with the expression of L-form hsp. In addition, Kupffer cells colonized by L-forms constitutively synthesized mRNA for interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α). These results suggest that conversion of S. typhimurium to L-forms in phagocytic cells builds up and maintains acquired resistance, conferred by live-cell vaccines of S. typhimurium, against murine typhoid. [ABSTRACT FROM AUTHOR]

We investigated the host defense mechanism in primary infection with Listeria monocytogenes in non-obese diabetic (NOD) mice at pre-diabetic stage showing an impaired responsiveness of the αβ T cells to T-cell receptor (TCR) triggering. The NOD mice showed a deteriorated resistance at the late stage after an intraperitoneal infection with L. monocytogenes compared with BALB/c and C57BL/6 mice as assessed by bacterial growth in organs. Consistent with our previous findings, a prominent increase in number of γδ T cells was evident at the early stage after infection, while generation of Listeria-specific αβ T cells was impaired in these mice. In vivo administration of anti-TCR γδ monoclonal antibody (mAb) allowed L. monocytogenes to grow exaggeratedly in the NOD mice. These results imply that γδ T cells may be mainly involved in protection against primary infection with L. monocytogenes in NOD mice. [ABSTRACT FROM AUTHOR]

Interleukin-10 (IL-10) is a cytokine that regulates various macrophage functions. To elucidate the involvement of endogenous IL-10 in the early stage of murine salmonellosis, we examined the effect of anti-IL-10 monoclonal antibody (mAb) administration on the host defence mechanism against Salmonella choleraesuis infection. The in vivo administration of anti-IL-10 mAb significantly enhanced host resistance at the early stage of Salmonella infection, as assessed by bacterial growth in the peritoneal cavity and the liver. Enhanced levels of monokine mRNA, including IL-1α, tumour necrosis factor-α (TNF-α) and IL-12, were observed from day I after infection in the peritoneal macrophages in anti-IL-10 mAb-treated mice compared with those in control mAb-treated mice. Mice treated with anti-IL-10 mAb exhibited significantly higher levels of interferon-γ (IFN-γ) in the peritoneal exudate's and major histocompatibility complex (MHC) class II expression on the peritoneal macrophages on days 3 and 5 after infection. Notably, in vivo anti-IL-10 mAb brought about an increment of γδ T cells in the peritoneal cavity at the early phase of infection, which was correlated with the expression of endogenous heat-shock protein 60 (HSP60), which is implicated as a potential ligand for γδ T cells, in the infected macrophages. Our results suggest that the neutralization of endogenous IL-10 accelerates some macrophage functions and, consequently, the activation of immunocompetent cells, including & grave;δ cells, at the early stage of infection, resulting in an enhanced host defence against Salmonella infection.Interleukin-10 (IL-10) is a cytokine that regulates various macrophage functions. To elucidate the involvement of endogenous IL-10 in the early stage of murine salmonellosis, we examined the effect of anti-IL-10 monoclonal antibody (mAb) administration on the host defence mechanism against Salmonella choleraesuis infection. The in vivo administration of anti-IL-10 mAb significantly enhanced host resistance at the early stage of Salmonella infection, as assessed by bacterial growth in the peritoneal cavity and the liver. Enhanced levels of monokine mRNA, including IL-1α, tumour necrosis factor-α (TNF-α) and IL-12, were observed from day I after infection in the peritoneal macrophages in anti-IL-10 mAb-treated mice compared with those in control mAb-treated mice. Mice treated with anti-IL-10 mAb exhibited significantly higher levels of interferon-γ (IFN-γ) in the peritoneal exudate's and major histocompatibility complex (MHC) class II expression on the peritoneal macrophages on days 3 and 5 after infection. Notably, in vivo anti-IL-10 mAb brought about an increment of γδ T cells in the peritoneal cavity at the early phase of infection, which was correlated with the expression of endogenous heat-shock protein 60 (HSP60), which is implicated as a potential ligand for γδ T cells, in the infected macrophages. Our results suggest that the neutralization of endogenous IL-10 accelerates some macrophage functions and, consequently, the activation of immunocompetent cells, including & grave;δ cells, at the early stage of infection, resulting in an enhanced host defence against Salmonella infection. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to study the γδ T-cell receptor repertoire and target specificity following stimulation of peripheral T cells of BALB/c mice with autologous or bacterial ligands. The expression of Vγ and Vδ chain families in T cells that had been expanded by stimulation in syngeneic mixed lymphocyte culture or with purified protein derivative (PPD) was determined by the semiquantitative DNA polymerase chain reaction (PCR) method. Responder T cells to either of these stimuli strongly expressed both Vδ5 and Vδ6 genes. However, addition of the ML 30 anti-murine heat shock protein (hsp) 60 monoclonal antibody (mAb) to the cell culture selectively inhibited only the expansion of Vδ5 T cells. A Vδ5 T-cell hybridoma (KMT-5), which recognized syngeneic splenic and fibrosarcoma Meth A cells but not allogeneic cells, was produced by cell fusion from autoreactive blast cells. Incubation of the KMT-5 hybridoma in the presence of ML 30 antibody blocked the stimulation of interleukin-2 (IL-2) secretion by syngeneic target cells. It was also found that the DNA of KMT-5 hybridoma and of the autoreactive γδ T cells contained the BALB/c invariant delta (BID) chain sequence. It is concluded from these results that BALB/c peripheral Vδ5 T cells recognize an autologous hsp 60 target specificity in a Vδgene restricted manner. We also propose that T cells of this V gene family may be involved in the immune surveillance of certain tumours and intracellular infections. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) causes severe opportunistic infection in immunocompromised hosts. The importance of conventional alphabeta T cells in protection against CMV infection has been well documented. However, the role of the second T-cell population (which express the gammadelta T-cell receptor) in CMV infection is not known. In the present study, we analysed the function and protective role of gammadelta T cells in a murine cytomegalovirus (MCMV) infection model. After intraperitoneal infection with MCMV, the number of gammadelta T cells increased in the liver and peritoneal cavity from day 3, and reached a peak on day 5. The gammadelta T cells showed an activated T-cell phenotype and predominantly expressed Vgamma1, which is known to be expressed by heat-shock protein 65 (hsp 65)-specific gammadelta T cells. Analysis of cytokine expression demonstrated that the MCMV-induced gammadelta T cells expressed interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) but not interleukin-4 (IL-4), implying their participation in the cell-mediated immune response against MCMV. Depletion of gammadelta T cells by anti-T-cell receptor (TCR) gammadelta monoclonal antibody (mAb) treatment resulted in significant increase of virus titre and decrease of IFN-gamma in the liver on day 3 after MCMV infection, which further supports the importance of gammadelta T cells in early protection against infection. Finally, the MCMV-induced gammadelta T cells produced IFN-gamma in vitro in response to hsp 65. Our results suggest that gammadelta T cells participate in early protection against MCMV infection through recognition of hsp 65 and production of IFN-gamma.

We have previously reported that heat-shock protein (hsp) 60-reactive T-cell receptor (TCR)gamma delta+ T cells appear in the peritoneal cavity during the early stage of infection with Listeria monocytogenes in mice. In this study, we examined the kinetics of TCR gamma delta+ T cells during listeriosis in F344 rats by flow cytometry using a V65 monoclonal antibody (mAb) directed to a constant determinant of rat TCR gamma delta chains. TCR gamma delta+ T cells significantly increased in the peritoneal cavity on day 6 and then decreased by day 10 after infection, in parallel with the kinetics of hsp60 expression in the peritoneal macrophages during listeriosis in F344 rats. Most of the early appearing TCR gamma delta+ T cells were of the CD4- CD8 alpha beta+ CD5+ lymphocyte function-associated antigen (LFA)-1 alpha high CD45RC- interleukin-2 receptor (IL-2R) alpha- phenotype, although a significant fraction of the TCR gamma delta+ T cells expressed CD8 alpha only. The increase in TCR gamma delta+ T cells during listeriosis was prominent in F1 (F344 x Lewis) rats but only marginal in Lewis rats, which was correlated with the expression level of hsp 60 in the peritoneal macrophages. The peritoneal TCR gamma delta+ T cells in naive F344 rats appeared to proliferate significantly in response to recombinant hsp 60 (rhsp 60) derived from Mycobacterium bovis bacillus Calmette-Guérin (BCG). These results imply that the early appearance of hsp 60-reactive TCR gamma delta+ T cells during listerial infection can be generalized across species.

We investigated the host defense mechanism in primary infection with Listeria monocytogenes in non-obese diabetic (NOD) mice at pre-diabetic stage showing an impaired responsiveness of the alpha beta T cells to T-cell receptor (TCR) triggering. The NOD mice showed a deteriorated resistance at the late stage after an intraperitoneal infection with L. monocytogenes compared with BALB/c and C57BL/6 mice as assessed by bacterial growth in organs. Consistent with our previous findings, a prominent increase in number of gamma delta T cells was evident at the early stage after infection, while generation of Listeria-specific alpha beta T cells was impaired in these mice. In vivo administration of anti-TCR gamma delta monoclonal antibody (mAb) allowed L. monocytogenes to grow exaggeratedly in the NOD mice. These results imply that gamma delta T cells may be mainly involved in protection against primary infection with L. monocytogenes in NOD mice.

Conversion of Salmonella typhimurium to L-forms, both in vitro and in vivo, resulted in the expression of proteins cross-reacting to the mycobacterial 65,000 MW heat-shock protein (hsp). Immunization of C3H/HeJ mice with a protective dose of stable L-form S. typhimurium induced gamma delta T cells in the liver, in accordance with the multiplication of L-form Salmonella in Kupffer cells. The number of gamma delta T cells decreased after the intracellular growth of L-form Salmonella plateaued. Persistance of the L-forms in Kupffer cells, however, allowed hepatic gamma delta T cells to increase within 48 hr of infection with virulent S. typhimurium. Thus, the intrahepatic colonization of L-form Salmonella seems to keep gamma delta T cells on standby, but the emergence of these T cells does not correlate with the expression of L-form hsp. In addition, Kupffer cells colonized by L-forms constitutively synthesized mRNA for interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha). These results suggest that conversion of S. typhimurium to L-forms in phagocytic cells builds up and maintains acquired resistance, conferred by live-cell vaccines of S. typhimurium, against murine typhoid.

Interleukin-10 (IL-10) is a cytokine that regulates various macrophage functions. To elucidate the involvement of endogenous IL-10 in the early stage of murine salmonellosis, we examined the effect of anti-IL-10 monoclonal antibody (mAb) administration on the host defence mechanism against Salmonella choleraesuis infection. The in vivo administration of anti-IL-10 mAb significantly enhanced host resistance at the early stage of Salmonella infection, as assessed by bacterial growth in the peritoneal cavity and the liver. Enhanced levels of monokine mRNA, including IL-1 alpha, tumour necrosis factor-alpha (TNF-alpha) and IL-12, were observed from day 1 after infection in the peritoneal macrophages in anti-IL-10 mAb-treated mice compared with those in control mAb-treated mice. Mice treated with anti-IL-10 mAb exhibited significantly higher levels of interferon-gamma (IFN-gamma) in the peritoneal exudates and major histocompatibility complex (MHC) class II expression on the peritoneal macrophages on days 3 and 5 after infection. Notably, in vivo anti-IL-10 mAb brought about an increment of gamma delta T cells in the peritoneal cavity at the early phase of infection, which was correlated with the expression of endogenous heat-shock protein 60 (HSP60), which is implicated as a potential ligand for gamma delta T cells, in the infected macrophages. Our results suggest that the neutralization of endogenous IL-10 accelerates some macrophage functions and, consequently, the activation of immunocompetent cells, including gamma delta T cells, at the early stage of infection, resulting in an enhanced host defence against Salmonella infection.

Anti-CD3 monoclonal antibody (mAb) has been administered in clinical organ transplantation to reverse acute allograft rejection; however, severe immunodeficiency can result from such mAb treatment and cause an increased incidence of opportunistic infections. Therefore, new model systems are required in order to establish better methods for suppressing allograft rejection while preserving resistance to opportunistic infections. In this study, we compared the effects of the in vivo administration of anti-T-cell receptor-alpha beta (TcR alpha beta) mAb, H57-597, with those of anti-CD3 mAb, 145-2C11. Much to our surprise, the in vivo administration of anti-TcR alpha beta mAb prior to skin grafting led to a longer allograft survival than that of anti-CD3 mAb at any of the comparable dosages examined. In the lymphoid organs of mice treated with anti-TcR alpha beta mAb, TcR alpha beta-bearing cells were almost completely depleted, while TcR gamma delta-bearing cells remained at a relatively increased level on day 14 after anti-TcR alpha beta mAb treatment. The in vitro stimulation by anti-TcR gamma delta mAb clearly showed that such TcR gamma delta-bearing cells were functionally intact. Furthermore, the mice treated with anti-TcR alpha beta mAb, but not anti-CD3 mAb, were observed to be resistant to infection with Listeria monocytogenes. Finally, treatment with H57-597, but not with 145-2C11, led to a marked prolongation of skin allograft survival in the thymectomized mice. These results strongly suggest that anti-TcR alpha beta mAb, which partially preserved anti-bacterial resistance, may be more effective in preventing graft rejection than anti-CD3 mAb in the periphery, and indicate that anti-TcR alpha beta mAb may thus be potentially applicable for human transplantation. In addition, these results also indicate that the TcR gamma delta-bearing cells alone, at least in the absence of TcR alpha beta-bearing cells, do not contribute to allograft rejection in vivo.

The purpose of this paper was to study the gamma delta T-cell receptor repertoire and target specificity following stimulation of peripheral T cells of BALB/c mice with autologous or bacterial ligands. The expression of V gamma and V delta chain families in T cells that had been expanded by stimulation in syngeneic mixed lymphocyte culture or with purified protein derivative (PPD) was determined by the semiquantitative DNA polymerase chain reaction (PCR) method. Responder T cells to either of these stimuli strongly expressed both V delta 5 and V delta 6 genes. However, addition of the ML 30 anti-murine heat shock protein (hsp) 60 monoclonal antibody (mAb) to the cell culture selectively inhibited only the expansion of V delta 5 T cells. A V delta 5 T-cell hybridoma (KMT-5), which recognized syngeneic splenic and fibrosarcoma Meth A cells but not allogeneic cells, was produced by cell fusion from autoreactive blast cells. Incubation of the KMT-5 hybridoma in the presence of ML 30 antibody blocked the stimulation of interleukin-2 (IL-2) secretion by syngeneic target cells. It was also found that the DNA of KMT-5 hybridoma and of the autoreactive gamma delta T cells contained the BALB/c invariant delta (BID) chain sequence. It is concluded from these results that BALB/c peripheral V delta 5 T cells recognize an autologous hsp 60 target specificity in a V delta-gene restricted manner. We also propose that T cells of this V gene family may be involved in the immune surveillance of certain tumours and intracellular infections.

The liver comprises unique T cells differentiating extrathymically and expressing an intermediate intensity of alpha beta T-cell receptor (TcR) and a high intensity of leucocyte function antigen-1 (LFA-1). To elucidate the functional roles of the intermediate alpha beta TcR cells in host defence against bacterial infection, we examined the effects of depletion of the intermediate alpha beta TcR cells by in vivo administration of monoclonal antibodies (mAb) to intercellular adhesion molecule-1 (ICAM-1)/LFA-1 and alpha beta TcR on the bacterial growth in the liver after infection with Salmonella chorelaesuis in mice. Pretreatment with mAb to LFA-1 (200 micrograms/mouse) together with mAb to ICAM-1 (200 micrograms/mouse), which could preferentially deplete the intermediate alpha beta TcR cells and gamma delta TcR cells in the liver, resulted in a severely reduced ability to resolve acute phase of Salmonella infection in the liver. Pretreatment with a low dose of anti-alpha beta TcR mAb (60 micrograms/mouse), which depleted only bright alpha beta TcR cells, did not affect the bacterial growth in the liver at the early stage after Salmonella infection, while the depleting of both intermediate and bright alpha beta TcR cells by pretreatment with a high dose of anti-alpha beta TcR mAb (120 micrograms/mouse) allowed the bacteria to multiply exaggeratedly in the liver at this stage. These results suggest that intermediate alpha beta TcR cells may play an important role in protection at the early stage after Salmonella infection in liver and that the interaction of ICAM-1/LFA-1 is critically involved in protective roles of extrathymic T cells bearing intermediate alpha beta TcR in liver at the early stage after Salmonella infection.

It has been shown that T-cell receptor (TcR) gamma delta + CD4- CD8- T cells increase in number and have an important role in early protection in murine Listeria monocytogenes infection. In this report, to characterize further the phenotype of the gamma delta T cells in listeriosis, we analysed V region gene usage and in vitro antigen recognition of the TcR gamma delta T cells in the peritoneal cavity of mice at the early phase after i.p. infection with a sublethal dose of L. monocytogenes. The gamma delta T cells predominantly expressed V delta 6 which has been reported to be expressed by TcR gamma delta-bearing foetal thymocyte hybridomas specific to mycobacterial and self heat-shock protein (hsp) 60. These early appearing CD3+ CD4- CD8- T cells in Listeria-infected mice, which were reported to be TcR gamma delta T cells, increased in proportion and in size by in vitro stimulation with recombinant hsp 60 from Mycobacterium bovis and purified protein derivative from M. tuberculosis but not by stimulation with heat-killed L. monocytogenes. A 65,000 MW molecule was detected in the lysate of viable L. monocytogenes but not in the lysate of heat-killed L. monocytogenes by a monoclonal antibody (mAb) raised against mycobacterial hsp 60. These results suggest that the V delta 6-bearing peripheral gamma delta T cells are activated by recognizing listerial hsp 60 expressed by viable L. monocytogenes. The hsp 60-reactive V delta 6-bearing T cells may have an important role in protection against L. monocytogenes and other parasites that express hsp 60 at high level.

L-selectin, which was first reported as MEL-14 antigen in mice, is a type of animal lectin and expressed on lymphocytes, neutrophils and macrophages. L-selectin has been reported to be a homing receptor of lymphocytes to peripheral lymph nodes and to have an important role in initial adhesion of lymphocytes and neutrophils to endothelial cells activated by inflammatory cytokines. On the other hand, it has been reported that naive T cells express L-selectin while memory T cells and in vitro antigen-stimulated T cells lose its expression. If all memory T cells lack L-selectin, trafficking of memory T cells into inflammatory sites would be difficult. To know whether all memory T cells lack L-selectin expression, kinetics of expression of L-selectin was analysed on memory T-cell subsets, which are detected by expression of CD44, in mice after intraperitoneal immunization with a sublethal dose of viable Listeria monocytogenes. T cells expressing both L-selectin and CD44 were detected in splenocytes and peritoneal exudate cells (PEC) from untreated mice, though at low levels. L-selectin+ CD44+ T cells increased in PEC, which are known to be highly enriched in antigen-primed T cells, and reached maximum level on day 14 after immunization. Furthermore, we found increases not only of L-selectin- CD44+ but also of L-selectin+ CD44+ T cells by in vitro Listeria antigen stimulation of Listeria-immune spleen cells on day 14. These results showed that T cells expressing both L-selectin and CD44 increase after antigen stimulation in vivo and in vitro. The L-selectin+ CD44+ T cells may be a subset of memory T cells which retain their capacity of trafficking to inflammatory sites.

Recombinant human granulocyte colony-stimulating factor (rh G-CSF) enhanced resistance of mice against Listeria monocytogenes (LM) as determined by survival and bacterial growth. Mice pretreated with rh G-CSF twice daily for 5 days survived better than untreated animals to the challenge with LM. Number of bacteria in peritoneal cavity (PC) and spleen was lower in treated mice than that in the control group. Rh G-CSF increased mainly polymorphonuclear cells (PMN) in blood and spleen. After LM inoculation, a larger number of PMN and monocyte-macrophages accumulated in PC and spleen of tested mice. In addition, PMN primed in vivo with rh G-CSF released more superoxide anions when stimulated with phorbol myristate acetate. The inhibition of bacterial growth in PC and spleen could be ascribed to the accumulation of phagocytic cells at the infection sites and the increased oxidative metabolism. The results provided further evidence of the important contribution of G-CSF and neutrophils, as target cells, to the host defence against the intracellular bacteria.

We have previously reported that T-cell receptor (TcR) gamma delta-bearing T cells precede TcR alpha beta-bearing T cells in appearance in the thymus after whole-body irradiation. In the present study, the kinetics of appearance of intestinal intra-epithelial lymphocytes (IEL) was examined in mice after whole-body irradiation with a lethal dose of 9.5 Gy or with a sublethal dose of 6 Gy. The number of CD3+ IEL decreased to the lowest value 4 days after irradiation with 9.5 Gy, and thereafter increased to half as many as the normal level by day 7. Thy-1+TcR alpha beta- IEL and Thy-TcR alpha beta- IEL recovered considerably by day 7 after the irradiation, whereas Thy-1+TcR alpha beta+ IEL and Thy-1+TcR alpha beta+ IEL hardly recovered at this stage. All mice died within 12 days after irradiation with a lethal dose of 9.5 Gy. On the other hand, when irradiation dose was decreased to 6 Gy, all mice survived beyond 40 days after irradiation. The number of CD3+ IEL recovered to the normal level by 10 days after irradiation with 6 Gy. Consistently with the results in mice irradiated with a lethal dose, the first cells to increase in IEL of mice irradiated with a sublethal dose were TcR gamma delta+ IEL expressing Thy-1 antigen. The number of Thy-1+TcR gamma delta+ IEL increased to approximately two-fold as many as that in normal mice by day 10, while TcR alpha beta+ IEL began to increase in number from day 20 after irradiation and recovered to the normal level by day 40 after irradiation. Thus, sequential appearance of TcR gamma delta+ and TcR alpha beta+ IEL was evident after irradiation, similar to that seen in the thymus after irradiation. The IEL on day 10 after a sublethal irradiation, which is composed mainly of Thy-1+TcR gamma delta+ IEL, exhibited a strong cytolytic activity against P815 in the presence of anti-CD3 mAb, suggesting that the early appearing Thy-1+TcR gamma delta+ IEL may play important roles in epithelial immunity at an early stage after irradiation.

In order to search for a possible role of abnormally proliferating T cells in developing autoimmune disease in lpr mice, and to define the difference of the T cells among various lpr-congeneic mice with different clinicopathological findings, the T-cell receptor (TcR) V beta gene expression in the enlarged lymph nodes (LN) of C3H/HeJ-lpr/lpr (C3H-lpr), C57BL/6-lpr/lpr (B6-lpr) and MRL/Mp-lpr/lpr (MRL-lpr) mice was analysed. A RNA blot analysis using several V beta-specific probes showed that the V beta 3 gene, whose products are important for recognizing Mlsb/a, was used in B6-lpr and MRL-lpr with the Mlsb/b but not in C3H-lpr with the Mlsb/a. The V beta 5 gene, which is selectively related to I-E molecules, was predominantly used in B6-lpr(I-E-) but not in C3H-lpr(I-E+) nor MRL-lpr(I-E+). Similarly, the V12 gene was also expressed in B6-lpr but not in C3H-lpr. To compare in detail in V beta repertoire among lpr mice with different major histocompatibility complex (MHC) backgrounds, the V beta gene sequences in the cDNA libraries from LN cells of C3H-lpr were analysed, following the recent investigation of B6-lpr mice (Ohga et al., 1989). Eleven beta-chain cDNA out of 32 beta cDNA in B6-lpr and 24 beta-chain cDNA out of 55 beta cDNA in C3H-lpr were found to contain sequences with open reading frames that potentially encode functional TcR beta-chain. The frequencies of the messages in the cDNA libraries from these mice were consistent with the RNA blot analysis using V beta 3- and V beta 5-specific probes. It was notable that 36% of the functional beta-chain mRNA in B6-lpr and 50% of the beta mRNA in C3H-lpr expressed the V beta 8 gene family. When the TcR V beta gene expression was compared between the LN cells in C3H-lpr, B6-lpr and MRL-lpr, as reported by Singer et al. (1986), the usage of V beta genes other than the V beta 8 gene family in B6-lpr (H-2b) LN cells differed significantly from those in C3H-lpr (H-2k) and MRL-lpr (H-2k). The results presented here indicate that the usage of V beta genes is heavily influenced by the genetic background of lpr mice, similar to normal mice, but with preferential usage of the V beta 8 gene family as a common structural feature in lpr gene-induced cell populations.

It has been reported previously that environmental antigens such as intestinal microflora play an important role in an age-associated increase in number of T-cell receptor gamma/delta-bearing T cells. To extend the scope of this finding, this study examined the influences of local inflammation on the accumulation and/or proliferation of gamma/delta T cells in athymic nude mice injected subcutaneously with complete Freund's adjuvants (CFA). The inguinal lymph nodes (ILN) in nude mice injected with CFA in their hind footpads 7 days previously contained an increased number of CD3+CD4-CD8- cells. Increased levels of proliferative responses against syngeneic stimulator cells were noted in the LN cells of CFA-injected nude mice in association with increases in expression of gamma- and delta-chain gene messages. Furthermore, the LN cells showed an early proliferative response to purified protein derivative (PPD) from Mycobacterium bovis. These results suggest that local inflammation by CFA may induce functional gamma/delta T cells in nude mice, which may proliferate rapidly at the inflamed sites and represent a first line of defence in such animals against the invasion of various pathogens.

Clonal deletion of T cells capable of recognizing both host-type Mls and donor-type Mls occurred in the peripheral mature T-cell pool in radiation bone marrow chimeras of two H-2-compatible Mls-disparate strain combinations of AKR/J(H-2k,Thy-1.1,Mls-1a) and C3H/He(H-2k,Thy-1.2,Mls-1b). In order to determine further the stage at which the clonal deletion occurs in thymus, we examined the kinetics of thymocytes bearing V beta 6 capable of recognizing Mls-1a in both C3H/He----AKR/J and AKR/J----C3H/He chimeras. An almost complete replacement from host-derived cells to donor-derived cells occurred by Day 21 after reconstitution in both chimeras. At this stage, CD4+CD8+ double-positive thymocytes contained an appreciable number of cells that expressed V beta 6 on their surface, albeit at low intensity, whereas CD4 or CD8 single-positive thymocytes which expressed a high density of V beta 6 were virtually abolished in both C3H----AKR and AKR----C3H chimeras on Day 21. These results suggest that clonal deletion of self-Mls-reactive T cells begins at an early stage when the thymocytes interact with the early appearing donor-derived haemotopoietic cells and relatively radio-resistant host-derived cells in thymus of radiation bone marrow chimeras.

Neonatally thymectomized (NTx) mice, whose ability to mount antigen-specific cell-mediated immunity is reported to be generally defective, were found to be capable of mounting a normal level of acquired cellular resistance (ACR) and delayed footpad reaction (DFR) to Listeria monocytogenes. The present study was done in order to determine the functional differences of T cells contributing to the protection against L. monocytogenes between NTx and sham-operated mice. In mice immunized with viable L. monocytogenes, the absolute number of splenic T cells was significantly lower in NTx mice compared with sham-operated mice. When the ability of immune T cells to transfer ACR and DFR was examined by passive transfer, lymphocytes from immune NTx mice conferred a higher level of ACR and DFR on naive recipient mice, despite the marked difference in total number of T cells compared with immune Sham mice. Antigen-specific proliferation and interleukin-2 (IL-2) production by splenic T cells from immune NTx mice were significantly lower than in those from immune Sham mice. The proliferative response of T cells to exogenous IL-2 was also lower in NTx group. These results suggest that the requirement for the IL-2-driven T-cell proliferation system is basically low in the generation of effector T cells specific for L. monocytogenes.

We have previously shown that extrathymic rearrangements of T-cell receptor (TcR) gamma and delta chain genes occur in the peripheral lymphoid tissues of athymic nude mice. To further determine where the TcR gene rearrangements occur in nude mice, we investigated the rearrangement and expression of the TcR genes in the long-term cultured bone marrow (LTBM) cells which were homogenous in developments without mature T cells as assessed by FACS analysis. The LTBM derived from euthymic mice contained TcR gamma and delta chain genes in germline configuration, while gene rearrangements of both locus were detected in the LTBM cells from nude mice. These results suggested that gamma and delta gene rearrangements do occur in the bone marrow cells of nude mice and that the T-cell precursors in bone marrow may be increased in frequency in such animals.

Delayed footpad reactions and acquired cellular resistance to Listeria monocytogenes were studied in mice whose mononuclear phagocyte system (MPS) had been blocked or stimulated. Colloidal carbon was used for the blockade of MPS and Corynebacterium parvum used for the stimulation. Strong delayed footpad reactions. On the other hand, the i.v. injection of 3 X 10(1) listeria induced an appreciable level mice, while in MPS-stimulated mice, i.v. injection with even 4 X 10(3) listeria could not induce such strong delayed footpad reaction. On the other hand, the i.v. injection of 3 X 10(1) listeria induced an appreciable level of delayed footpad reaction only in MPS-blocked mice. Acquired cellular resistance was depressed by MPS stimulation, whereas it was augmented by MPS blockade. These results suggested that non-specific activity of MPS modulates subsequent immune responses after inoculation of listeria.