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Activation of fresh blood lymphocytes has been measured by uptake of tritiated thymidine, following exposure to irradiated cells from autochthonous or allogeneic cell lines (LCL cells). Nine autochthonous combinations were studied. In every case activation was observed and in one the rate and peak level of activation were comparable to those found in control allogeneic mixtures. Neither foetal calf serum nor antibiotics appeared to be important factors in the activation process. There was no correlation between the number of identified HL-A histo-incompatibilities in a given allogeneic mixture and the rate or peak level of activation achieved. Activation appears to be influenced by the metabolic state of the LCL cells and the rate of the reaction is sensitive to the precise culture conditions under which it proceeds. Some distinction can be drawn between the antigens responsible for activation in autochthonous and in allogeneic mixtures but the former may prove to be modified histocompatibility determinants. [ABSTRACT FROM AUTHOR]

Cells from thirty-three human lymphoid cell lines and sublines have been typed for HL-A antigens by a microcytotoxicity test. Similar patterns of HL-A antigens were found for the cell line cells and for the fresh lymphocytes of the donor of the line (eleven cases). However, certain typing sera gave positive reactions with the cell line cells which were not found with the fresh lymphocytes. No correlation was noted between the pattern of these 'extra' reactions and the HL-A typing of the cells. These same typing sera often gave positive reactions with blood lymphocytes cultured for several days in conventional media. These positive reactions were quantitatively more pronounced and sometimes qualitatively different if the cells had been stimulated. A range of normal sera failed to react with cell line cells suggesting that the HL-A typing sera giving 'extra' reactions are detecting antigens in some way related to a histocompatibility system. Absorption studies performed with two of the lines confirmed the HL-A typing by the direct cytotoxicity test. Two sera giving 'extra' reactions were also tested in the absorption experiments. The results indicated that antibodies other than those of the HL-A specificity designated for these sera were responsible for the 'extra' reactions. It is suggested that 'extra' reactions indicate a change in the apparent antigenic expression of lymphoid cells reflecting altered membrane characteristics as they adapt to a culture environment. [ABSTRACT FROM AUTHOR]

Optimum conditions have been found for a specific quantitative absorption of mouse lymphocytes on to allogeneic target cells. Using this technique, it has been established that C3H anti-A lymphocytes immune to the specificities of a single H-2 sub-locus (D) were absorbed neither on cells bearing only some of the components of the immunizing complex (DBA/1 and I/St targets) nor on their mixture. Conversely, C57BL anti-A lyrnphocytes immune to the specificities of two H-2 sub-loci (D and K) reacted separately with each of the components on corresponding third-party targets (B10.D2(H-2d) and C3H (H-2k) as shown both by the direct cytotoxic effect and by the quantitative absorption technique. The results of absorption of these lymphocytes on mixtures of B10.D2 and CSH target cells used in various proportions indicate that C57BL anti-A lymphocytes represent a mixture of two 'polyvalent' populations in ratio of 1:3. This, together with the previous data indicates that 'committed' lymphocytes may be 'polyvalent' and that the initial recognition step of H-2 antigens may result from a direct contact between membranes of grafted cells and 'unprimed' host lymphocytes. Structural matching of the membrane antigenic complex and of normal and immune lymphocytes is suggested as a decisive factor of immunological recognition initiation in a transplantation context. [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]

The serum haemolysin response was studied in rats which had been subjected to a suppressive whole-body dose of γ-irradiation followed after 24 hours by an intravenous injection of sheep erythrocytes. A standard restorative dose of syngeneic thoracic duct lymphocytes was given immediately after the antigen or after a variable delay. Delays of 12, 24, 48 and 72 hours were followed by progressively smaller haemolysin responses. These observations suggested that the recruitment of lymphocytes begins very soon after the injection of sheep erythrocytes and that the inductive influence of the antigen wanes steadily so that the effective period of recruitment probably lasts for 1–2 days. [ABSTRACT FROM AUTHOR]

Cells from lymph nodes or spleen, or peripheral blood leucocytes of immunized guinea-pigs were cultured in the presence of antigens or phytohaemagglutinin. Significant incorporation of tritiated thymidine occurred in a variable proportion of the experiments with lymphocytes from each of the three sources. Cells taken from animals that had been immunized with sheep erythrocytes with adjuvant, and which showed strong delayed hypersensitivity, and from animals immunized intravenously with sheep erythrocytes, which failed to show delayed hypersensitivity reactions, both responded to sheep erythrocytes in vitro. Cells from guinea-pigs immunized with complete Freund's adjuvant alone, which showed strong delayed hypersensitivity to tuberculin PPD, gave more positive responses in vitro than did cells taken from animals which received an intravenous injection of tuberculin PPD before the adjuvant. These animals showed no or weak delayed hypersensitivity reactions (immune deviation). The immunological significance of the in vitro proliferative reaction is discussed.

The incidence of a thymocyte-specific antigen in thymuses of rats at different ages was studied by immunofluorescence using an anti-thymus microsome serum. This serum, which could detect an antigen common to all lymphocytes, was made thymus-specific by absorption with non-thymic lymphoid organs. The thymic antigen was detected in the earliest embryo (32 mm) in which lymphoid cells are recognizable in the thymic anlage, where it appeared to be present in all thymic lymphocytes. With increasing age, both the proportion of lymphoid cells bearing the antigen and the amount of antigen present were decreased. In lethally irradiated marrow-injected animals, the thymus recovered its normal histology and lymphoid antigenicity within a month, but the thymocyte-specific antigen did not reappear. The findings suggest that the antigen is an exclusive component of native thymic lymphocytes. [ABSTRACT FROM AUTHOR]

Albino guinea-pigs were actively sensitized with complete Freund's adjuvant. Tuberculin skin reactivity and tuberculin-induced in vitro mitotic responsiveness of circulating lymphocytes were determined sequentially in each animal after sensitization. In nine of ten animals studied, both skin reactivity and in vitro mitotic response to tuberculin appeared 3 weeks after sensitization. [ABSTRACT FROM AUTHOR]

Cultures were set up of white cells from patients with oral ulceration and from control subjects. The effects of saline extracts of foetal oral mucosa, liver, skin, colon, striated muscle and salivary gland on DNA synthesis by lymphocytes in the cultures were determined by measuring their uptake of [14C] thymidine. The results showed stimulation by oral mucosa, and to a lesser degree by skin, almost exclusively in patients with recurrent aphthous ulcers; colon and salivary gland stimulated the lymphocytes of occasional individuals regardless of the type or presence of oral ulceration, and liver produced a similar effect, but stimulated lymphocytes in a higher proportion of patients with aphthous ulcers. Specific stimulation by oral mucosa was increased during phases of ulceration and diminished during remissions. It is suggested that lymphocyte transformation (indicated by [14C]thymidine uptake) in patients with recurrent aphthous ulceration is the result of specific antigenic stimulation of a portion of the lymphocyte population following previous encounter with an oral mucosal antigen. [ABSTRACT FROM AUTHOR]