THE DIFFERING SURVIVAL OF NORMAL AND SENSITIZED SPLEEN CELLS TRANSFERRED TO ALLOGENEIC HOSTS

Effect of iodoacetate on T lymphocytes of young AKR mice

The influence of sulphydryl inhibitor iodoacetate on properties characteristically associated with T-lymphocytes was examined in young AKR mice. Thymocytes from mice receiving 100 microgram of iodoacetate showed a decrease in cortisone sensitivity, and responded more vigorously to phytohemagglutinin (PHA). Spleen cells from treated mice also exhibited greater reactivity to both PHA and concanavalin A (Con A). The uptake of 14C-iodoacetate by the thymus, spleen, lymph nodes, bone marrow, liver and kidneys also was investigated. One hour, 2 h and 18 h after the intraperiotoneal injection of 10-3 M iodoacetate, the thymus demonstrated a higher incorporation of the labelled compound than did the spleen, lymph nodes or other organs examined. These findings provide further evidence to indicate that the immuno-enhancement observed following iodoacetate treatment is related to its effect on T lymphocytes.

Binding of heterologous anti-brain antibodies to mouse B cells

Antibodies produced in rabbits against mouse brain are able to react with the majority of lymph node and spleen murine lymphocytes, as demonstrated by indirect immunofluorescence. Cells stained by a suitably absorbed rabbit anti-mouse brain serum showed various degrees of fluorescence, from bright fluorescent rings to a few speckles per cell; lymphocytes from the spleen of deprived mice (B mice) predominantly stained in small caps. Double labelling experiments in which B cells were identified by their 'easily detectable' surface immunoglobulin revealed that a great proportion of these cells had two overlapping caps, a large one formed by the anti-immunoglobulin serum and a small one formed by the anti-brain serum. Up to 10 per cent of these spleen B cells, however, appeared as strongly fluorescent as T cells, with the suitably absorbed heterologous anti-brain serum. No anti-immunoglobulin activity was detected in this serum. It is therefore suggested that some B cells may bear on their surfaces a theta or theta-related antigen similar to that on T cells.

Identification of hamster thymus-derived lymphocytes employing rabbit anti-hamster brain serum

Rabbit anti-hamster brain sera prepared from the brains of Syrian and Chinese hamsters were evaluated for their potential to identify thymus-derived lymphocytes present in these animals. The unabsorbed antisera were cytotoxic in vitro for both homologous and heterologous thymocytes and splenocytes. Following absorption with hamster liver and erythrocytes, the antisera remained toxic for thymocytes, but were less toxic for splenocytes. Comparative testing of both the rabbit anti-Syrian and anti-Chinese brain sera with rabbit anti-C3H mouse brain serum indicated that considerable cross-reactivity exists between the different anti-brain sera. The in vivo administration of any of the antisera to C3H mice resulted in a lowered titer to the thymus-dependent sheep erythrocyte antigen response as measured by the hemolysis-in-gel technique. In vitro treatment with the anti-brain sera had no effect on plaque-forming cells present in the spleen.

In vivo effects of rabbit anti-mouse brain serum on theta bearing lymphocytes of AKR mice

The in vivo effect of rabbit anti-AKR mouse brain-associated serum (RAMB) was determined on theta bearing lymphocytes present in the spleens and thymuses of mature C3H mice and AKR mice staged into preleukemic, leukaemic and overtly leukaemic states. Following seven daily injections of RAMB serum, the splenic plaque-forming cell (PFC) response to sheep erythrocytes (SRBC) and the percentage of theta-bearing lymphocytes in the spleen were significantly decreased in the C3H and the preleukaemic AKR mice. Decreases in thymic weight and thymocyte numbers were also apparent. Determinations of theta antigen density using in vitro cytoxicity tests indicated that splenic and thymic T lymphocytes (thymus-derived) remaining in the RAMB-treated C3H and preleukemic AKR mice consisted primarily of cells bearing less of the theta surface antigen. Histopathological studies of tissues from these two treated groups revealed cortical lymphocyte depletion in the thymus, and marginal and periarteriolar depletion in the spleen. Leukaemic AKR mice, administered seven injections of RAMB serum, demonstrated less dramatic changes in thymus weight, histopathology and theta-bearing cell percentages when compared with the data from the preleukaemic AKR or matureC3H mice. The results from testing overtly luekaemic AKR mice administered RAMB serum for the 7 or 9 days did not demonstrate differences from findings from groupsof overtly leukaemic control mice. These data indicate that the in vivo activity of RAMB serum in C3H mice and preleukaemic AKR mice is directed primarily toward the less mature T-lymphocyte population. This influence of RAMB serum is lesspronounced in leukaemic and the more overtly leukaemic mice, suggesting that a decreasedpopulation of RAMB-susceptible lymphocytes are present in these animals.

Antigenic characterization of murine rosette and plaque-forming cells

Specific antisera reacting with mouse B and T lymphocytes were raised by immunizing rabbits with: (1) mouse myeloma tumour cells; (2) bone-marrow cells; (3) thymus cells, and proper absorptions of the antisera obtained. These antisera together with anti-IgG and anti-θ were used to characterize surface antigens on antibody-producing cells. It was found that anti-bone marrow serum, absorbed with thymus cells in the presence of guinea-pig C, completely inhibited in vitro the action of all types of antibody-producing cells, i.e. direct and indirect PFC, and normal and immune-RFC. Anti-myeloma serum absorbed with thymus cells inhibited direct and indirect PFC, most of the immune-RFC, but did not inhibit normal RFC. Absorption with both thymus and bone-marrow cells rendered the anti-myeloma serum specific for an antigen present on PFC and myeloma cells (My antigen). Anti-IgG completely inhibited both normal and immune RFC but had only a minor inhibitory effect on PFC. On the other hand, antithymus absorbed with bone marrow cells, like anti-θ, did not inhibit PFC, and occasionally inhibited a small percentage of RFC. With the aid of these heterologous antisera at least three antigenic determinants could be defined on the surface of antibody-producing B lymphocytes: B1, B2 and My. Thus, normal-RFC were shown to be antigenically different from immune-RFC and both lack an antigen present in PFC. In addition, all these cells contained the B1 antigen, which was partially or completely missing from myeloma tumour cells.

Antigenic changes in lymph-node cells after administration of antiserum to thymus cells

Mice of the RIII and C57BL strains were treated with rabbit antiserum to thymus (ATS), and cells of their lymph nodes were analyzed serologi-cally at intervals after treatment. While lymph-node cells of untreated mice were sensitive to the cytotoxic effect of isoantibodies against the theta antigen, lymph-node cells of ATS-treated mice showed a significantly reduced sensitivity. Three days after ATS treatment lymph-node cells of most mice were completely refractory to the cytotoxic effect of theta antibodies. Administration of normal rabbit serum elicited only a slight reduction of the sensitivity of lymph-node cells to the cytotoxic effect of theta antibodies. The results support the hypothesis that ATS treatment selectively affects a population of thymus-dependent circulating lymphocytes.

Serological analysis of thymus and spleen grafts

Thymus and spleen grafts from neonatal C57BL mice were implanted beneath the kidney capsule of (A x C57BL) F(1) hybrids. At various intervals after implantation, the grafts were analyzed serologically. Cells of each graft were tested for the presence of cells of host origin, TL (thymus-leukemia) antigenicity, and sensitivity to the cytotoxic effect of guinea pig serum (GPS). Thymus grafts showed partial repopulation by host cells 11 days after grafting, and some grafts were completely repopulated by host cells 13 days after grafting. All thymus grafts were fully repopulated 18 days after grafting. With one exception, thymus grafts contained no significant number of TL-positive cells within 14 days after grafting. TL-positive cells appeared in thymus grafts examined 15 days after implantation, and their number increased up to the 18th day after implantation. Cells residing in thymus grafts remained sensitive to GPS throughout the period of observation. The acquisition of thymus-distinctive serological properties by host cells repopulating thymus grafts was similar in intact and in thymectomized recipients. Spleen grafts were completely repopulated by host cells as early as 8 days after grafting. The cells residing in spleen grafts remained TL-negative throughout the period of observation, and were refractory to the cytotoxic effect of GPS. It is thus apparent that, while both spleen and thymus grafts are invaded by TL-negative cells, only those entering the thymus acquire the antigen. The nature of the process by which the thymus endows thymus-distinctive properties on cells entering it is discussed.

Lymphoid-specific antigen: distribution and behaviour

The distribution of a lymphoid-specific antigen has been studied by immunofluorescence in the thymus and other lymphoid organs of the rat and in the thymuses of other vertebrate species. It was demonstrable in all rat lymphocytes except those of the bone marrow. The thymic lymphocytes of all warm-blooded vertebrates also reacted with the lymphoid-specific serum. Plasma cells in antigenically stimulated lymph nodes did not seem to possess the antigen but similar cells appearing in lymph nodes of rats which had been irradiated and injected with marrow cells of the same strain showed a strong reaction with the antiserum. The antigen is depleted in human and murine leukaemic lymphocytes. X-irradiation did not appear to affect the antigen significantly in cells surviving the treatment.

HISTOCHEMICAL AND ELECTRON MICROSCOPIC STUDIES OF THE LIVER IN RUNT DISEASE

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