Peritoneal Exudate Lymphocyte

Abstract The antigen-induced in vitro lymphocyte proliferative response of peritoneal exudate lymphocytes (PEL) from guines pigs immune to horseradish peroxidase (HRPO) has been studied. PEL can be stimulated after only a brief (60 min) exposure to HRPO in vitro at 37°C, and the amount of measured stimulation is equivalent to that produced by an equal concentration of antigen present continuously in culture. Lymphocyte stimulation is maximal when the short antigen exposure takes place at 37°C, but a small amount of stimulation is produced when PEL are exposed to antigen at 4°C. This reaction appears to require a separate antigen-binding cell rather than direct binding of antigen to the antigen responsive lymphocyte since PEL that have been pulsed with antigen can stimulate non-pulsed PEL when the two are mixed together. This antigenbinding cell does not have to divide in order to function since it is not sensitive to mitomycin-C, but must be viable. The antigen-binding cell does not have immunologic specificity since antigen-pulsed PEL from non-immune animals function as well as PEL from immune animals in inducing lymphocyte proliferation in non-pulsed PEL. Several different lymphoid populations were analyzed for the presence of cells capable of binding HRPO and activating immune PEL. Two highly purified thymus-derived (T) cell populations, lymph node lymphocytes and thymocytes contained no antigen-binding cells detectable by this technique. In addition, a bone marrow-derived lymphocyte population, guinea pig L2C leukemia cells, contained no detectable HRPO-binding cells. However, both monocyte- and macrophage-enriched populations contained large numbers of HRPO-binding cells. These data suggest that even in a purified lymphocyte population, macrophages or monocytes are the primary antigen-binding cells for the induction of T lymphocyte proliferation, in vitro.