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Normal IgG preparations of human, rabbit or guinea-pig origin (IgG2) were tested for their capacity to inhibit the cytotoxicity of purified human lymphocytes, as induced by rabbit IgG antibodies to chicken erythrocytes. All IgGs were found to be about equally efficient inhibitors. Human F(ab′)2 used for control, gave no inhibition. Human myeloma proteins of subclasses IgG1, IgG2 and IgG3, were about equally efficient inhibitors. In contrast, the inhibitory action of myeloma proteins belonging to subclass IgG4 was weak and more irregular. In this assay system, a large excess (∼ 106 × ) of normal IgG over antibodies had to be added in order to achieve ≥ 50 per cent inhibition. Heating of the inhibitors to 63° for 30 minutes did not significantly enhance their inhibitory capacity. For comparison, the same human IgG preparations and myeloma proteins were also tested for their capacity to inhibit phagocytosis by human blood monocytes of chicken erythrocytes sensitized with rabbit IgG antibody. As was to be expected in this system, only HGG, IgG1 and IgG3 caused inhibition whereas F(ab′)2, IgG2 and IgG4 were completely negative. [ABSTRACT FROM AUTHOR]

The cytotoxic effect of normal human blood lymphocytes on Chang cells in tissue culture was investigated. Cell damage was measured by release of 51Cr from pre-labelled tissue culture ‘target’ cells. This method was sensitive and rendered highly reproducible results. Released 51Cr was not re-utilized. About 25 per cent of the 51Cr was spontaneously released from labelled Chang cells when incubated for 24 hours at 37°. Lymphocytes at a lymphocyte/Chang cell ratio of 25:1 led to a slight increase of this release. When phytohaemagglutinin was also present, about 50—60 per cent of the isotope appeared in the medium. Under these conditions target cells were significantly damaged -within 1 hour. At a lymphocyte/Chang cell ratio of only 1:1, weak cytotoxic effects were also noted after 24 hours of incubation. The results of dose—response experiments suggested that a considerable proportion of the lymphocytes participated in the reaction. Individual variation of the cytotoxic effect of lymphocytes from different donors suggested that it could be related to the degree of histoincompatibility between lymphocytes and Chang cells. Under the present conditions contaminating erythrocytes or granulocytes did not interfere with the cytotoxic action of the lymphocytes.

Blood lymphocytes from thirteen patients with CLL were studied for surface-bound Ig (SIg), Fc receptors (EA rosettes), receptors for sheep erythrocytes (E rosettes) and receptors for Helix pomatia A haemagglutinin (FTP), a carbohydrate-binding protein with specificity for N-acetyl-D- galactosamine and related sugars. Fluorescein-labelled HP binds to subpopulations of human peripheral blood lymphocytes (PBL) treated with neuraminidase. In normal peripheral blood, HP binds to the T-lymphocytes while the majority of the B cells bearing surface-bound immunoglobulin do not have receptors for HP. In untreated CLL, HP binds to 90-100% of the neur-aminidase-treated PBL. Almost all of the SIg-positive cells in CLL patients also have receptors for HP. Two groups of patients were found: in one the total fraction of SIg+ cells was ⩽50% and about 30% of these lost their Ig during incubation at 37° C. No such loss of Slig was revealed in the remaining patients where total SIg+fraction was ≈70%. These patients usually had higher blood lymphocyte counts, probably reflecting a more advanced disease. CLL patients in remission with low numbers of leukaemic cells also had low numbers of blood lymphocytes carrying both SIg and HP-receptors. It is concluded that leukaemic cells carry both HP receptors and SIg. Testing of this combination therefore provides a valuable new tool for monitoring patients with CLL. [ABSTRACT FROM AUTHOR]

Human lymphocytes, activated by PHA or PPD, damage homologous cells in tissue culture, as shown by release of radioactivity from target cells labelled with 51Cr-chromate. Cytotoxic effects of supernatants from activated lymphocytes are difficult to demonstrate by this method. However, such supernatants inhibit the incorporation of radioactive amino acids into homologous and heterologous target cells. In this investigation the cytopathic effects of supernatants from human lymphocytes, stimulated with PHA or PPD, and that of the stimulated lymphocytes themselves were quantitatively assessed by four different methods. Established cell lines of human (Chang and HeLa cells) or mouse origin (L-cells) were used as target cells. Cytotoxic effects of supernatants were demonstrated in a micro modification of the cell counting assay. Supernatants also inhibited incorporation of 14C-leucine or 14C-thymidine into target cells. However, when assayed by release of 51Cr, this cytotoxic effect was usually weak or absent. In contrast, stimulated lymphocytes showed strong cytotoxicity in the chromium assay. The results suggest that stimulated human lymphocytes release factors which are not primarily cytolytic but which inhibit target cell metabolism and proliferation, eventually leading to cell death. [ABSTRACT FROM AUTHOR]

The antigen-induced DNA synthesis in vitro in lymphocytes from patients with acute Plasmodium falciparum malaria was investigated. The patients and healthy controls from Sweden or Colombia were the same as those studied in the accompanying paper (Troye-Blomberg el al., 1983). The malarial antigens used were sonicated membrane preparations or purified and concentrated supernatants from in vitro cultures of P. facliparum, similar preparations derived from normal human erythrocytes served as control antigen. In the patients' lymphocytes P. falciparum antigens induced a weak or moderate but significant stimulation of DNA synthesis, peaking after 3-4 days of incubation. This early response was specific for P. faleiparum since it was not obtained with lymphocytes from healthy donors nor with those from patients with acute P. vivax or P. ovale malaria. No antigen-induced response was seen in about half of the P.falciparum patients. However in a few negative eases, available for consecutive testing, positive reactions were seen with lymphocytes taken 2 weeks after infection when the blood of these patients was free of parasites. The early response induced in patients' lymphocytes to the P. falciparum antigens was not obtained with RBC antigen, however, these preparations frequently induced a response rising to significant levels later during incubation (day 5-6)- Similar delayed responses were obtained when either- patients' or control donors' lymphocytes were exposed to the P. falciparum antigens. This indicates that both the RBC and the parasite preparations contained mitogenic substances affecting human lymphocytes in general and easily obscuring the P, falciparum specific responses seen only in the patients. This latter response was relatively low and short lived, suggesting that it reflected a secondary in vitro stimulation of in vivo primed lymphocytes and that it was regulated by suppressor mechanisms. [ABSTRACT FROM AUTHOR]

The mitogen-induced DNA synthesis in vitro in lymphocytes from 20 patients acutely ill with Plasmodium falciparum malaria was compared with that of 16 healthy donors. Within both groups part of the donors were individuals who had only experienced short exposure or none at all to the parasite (Sweden) while the other part were donors living in a malaria endemic area (Colombia), The proliferative response to the T cell mitogen La (leucoagglutinin from PHA) of the patients was significantly reduced as compared with that of the controls. With pokeweed mitogen which stimulates T cells and induces a T cell-dependent activation of B cells, no difference between patients or controls was seen. The results were similar for the donors of different geographical origin and malaria background. Lymphocytes and monocytes from the peripheral blood of these donors were also studied for surface marker distribution by means of monoclonal antibodies. Both the absolute and the relative frequencies of T cells in the blood of the malaria patients were significantly reduced as compared with the controls. Furthermore, in almost all eight patients tested, the ratio between T4+ T cells (including the helper/inducer subsets) and T8+ T cells (including the suppressor and cytotoxic subsets) were below 1: 1 while they were close to 2:1 in the controls. The results indicate that the relative frequency of T8+ T cells, expressed as percentage total T cells (T.3+ ) was significantly elevated in the P. falciparum patients. The possible relationship between this imbalance and the irregular La response of the patients lymphocytes requires further investigation of lymphocyte function. [ABSTRACT FROM AUTHOR]

The cytotoxic functions of highly purified blood lymphocytes from patients with breast cancer were studied before and after radiotherapy. Addition of PHA or of rabbit antibodies to target cells (chicken erythrocytes) were chosen as two means of inducing lymphocyte cytotoxicity in vitro. The proportion of T and non-T lymphocytes was determined by means of E and EAC rosette tests. The antibody-induced cytotoxicity of lymphocytes decreased following radiotherapy while that mediated by PHA remained unchanged. There was some reduction in the percentage of EAC rosette-forming cells. These results, as well as our earlier observations, suggest that the decrease in the peripheral blood of the proportion of lymphocytes with receptors for activated complement is responsible for changes in the antibody-mediated lymphocyte cytotoxicity. [ABSTRACT FROM AUTHOR]