Splenocyte

Abstract: A new monoclonal mouse antibody that recognizes a subset of rat peripheral T cells has been prepared by immunizing mice with rat thymocyte glycoprotein. This antibody, designated MRC OX 8, labels all peripheral T cells that are unlabeled by the previously described W3/25 monoclonal antibody. No peripheral T cells were found that bound both antibodies, but, in contrast, 90% of thymocytes were doubly labeled. Thoracic duct lymphocytes of congenitally athymic nude rats were not labeled by either antibody, but the spleens of such animals contained both W3/25+ cells and MRC OX 8+ cells. These splenocyte subpopulations did not overlap. Using the fluorescence-activated cell sorter to isolate cells binding MRC OX 8 antibody, the phenotype of T cells mediating various T cell functions was established. Combining the present results with those published previously, it is shown that the cells providing help for antibody responses and those mediating graft-vs.-host reactions are phenotypically W3/25+ MRC OX 8-. On the other hand, parental T cells that suppress antibody formation in F1 hosts were identified as W3/25- MRC OX 8+. The relationship between the rat T cell subsets defined by these antibodies and those in the mouse identified by the Ly series of alloantibodies is discussed and a comparison made between teh rat W3/25+ subset and a recently identified human T cell subset.

Abstract: BALB/c mice develop specific and relatively long lasting immunity after exposure to sublethal numbers of viable Listeria monocytogenes. This immunity can be passively transferred to naive recipients with maximal protection conferred by spleen cells obtained from donors 6 days after immunization. Immunity that can be directly transferred to syngeneic recipients is surprisingly short lived. Cell recipients lose immunity as early as 72 hr after transfer, and recipients express no detectable immunity after 1 wk. This short lived immunity requires both L3T4+ and Lyt-2+ T cell populations for full expression. Both the level of immunity transferred and the duration of the protective response expressed in recipients are dramatically increased if the spleen cell population is cultured in vitro with concanavalin A before cell transfer. Recipients of concanavalin A-activated cells express antigen-specific levels of immunity increased 100- to 1000-fold compared with syngeneic recipients of directly transferred immune spleen cells. In addition, this elevated level of adoptively transferred immunity remains constant for at least 8 wk. Transfer of this culture-enhanced immunity requires only an Lyt-2+ T cell population and is not influenced by cells of the L3T4+T cell subpopulation. Both direct as well as culture-enhanced transfer of immunity require major histocompatibility complex-compatible recipients. These findings suggest that two phenotypically distinct T cell subpopulations function in the development of the immune response to L. monocytogenes and that only one cell subpopulation is required for expression of immunity to this intracellular parasite.

Abstract: Induction of stroke not only produces local ischemia and brain damage, but also has profound effects on peripheral immune responses. In the current study, we evaluated effects on spleen and blood cells 4 days after stroke induction. Surprisingly, there was a less inflammatory cytokine profile in the middle cerebral artery occlusion-affected right brain hemisphere at 96 h compared with earlier time points. Moreover, our results demonstrate that stroke leads to splenic atrophy characterized by a reduction in organ size, a drastic loss of splenocyte numbers, and induction of annexin V+ and TUNEL+ cells within the spleen that are in the late stages of apoptosis. The consequence of this process was to reduce T cell proliferation responses and secretion of inflammatory cytokines, resulting in a state of profound immunosuppression. These changes produced a drastic reduction in B cell numbers in spleen and blood, and a novel increase in CD4+FoxP3+ regulatory T cells. Moreover, we detected a striking increase in the percentage of nonapoptotic CD11b+ VLA-4-negative macrophages/monocytes in blood. Immunosuppression in response to brain injury may account for the reduction of inflammatory factors in the stroke-affected brain, but also potentially could curtail protective immune responses in the periphery. These findings provide new evidence to support the contention that damage to the brain caused by cerebral ischemia provides a powerful negative signal to the peripheral immune system that ultimately induces a drastic state of immunosuppression caused by cell death as well as an increased presence of CD4+FoxP3+ regulatory T cells.

Abstract: Anti-cytokine antibodies that block interactions between cytokines and cytokine receptors have been used to inhibit endogenous cytokine function. However, injection of mice with mixtures of IL-4 and either of two neutralizing anti-IL-4 mAb, at a cytokine/anti-cytokine mAb molar ratio of approximately 2:1, enhances and prolongs in vivo IL-4 activity, as measured by induction of increased spleen cell Ia expression. Although splenocyte Ia expression returns to baseline two days after mice are injected with free IL-4, soluble IL-4-anti-IL-4 mAb complexes still induce several-fold increases in Ia expression 3 days after injection. Complexes that contain as little as 400 ng of IL-4 have considerable in vivo stimulatory activity, and a maximal effect on splenocyte Ia expression is induced by injection of 2 micrograms of complexed IL-4. The stimulatory effect of IL-4-containing complexes on splenocyte Ia expression can be blocked by increasing the ratio of anti-IL-4 mAb to IL-4, by injection of anti-IL-4R mAb, and by in vivo aggregation of the complexes. Complexes of IL-4 with a non-neutralizing anti-IL-4 mAb do not have increased IL-4 agonist activity in vivo. These observations are most consistent with the possibility that neutralizing anti-IL-4 mAb act as carrier proteins that increase the in vivo half-life of IL-4 by preventing its excretion, and possibly, by preventing modification of its active site. The enhanced agonist effect of IL-4-anti-IL-4 mAb complexes is not unique; complexes of IL-3 with a neutralizing anti-IL-3 mAb have a greatly increased ability, compared with free IL-3, to stimulate mucosal mastocytosis, and complexes of IL-7 with a neutralizing anti-IL-7 mAb have a greatly increased ability, compared with free IL-7 or IL-7 complexed with a non-neutralizing anti-IL-7 mAb, to stimulate an increase in pre-B cell number. These observations suggest that complexes of cytokines and neutralizing anti-cytokine mAb may provide a generally useful way to increase the magnitude and duration of cytokine effects in vivo.