Specific binding of T lymphocytes to macrophages. III. Spontaneous dissociation of T cells from antigen-pulsed macrophages

Peritoneal exudate lymphocytes (PEL) from immune guinea pigs that adhere to antigen-pulsed macrophages (M∅) were cultured for 1 week to yield a population enriched in antigen-specific (selected) T cells. These cells bind specifically within hours to fresh autologous antigen-pulsed M∅. The dissociation of these selected PEL from antigen-pulsed M∅ was studied. No evidence was obtained that factors in the culture medium play a role in dissociation. Lymphocytes that have dissociated from antigen-pulsed M∅ are usually fully capable of rebinding to M∅ freshly pulsed with antigen, suggesting that there is no deficiency in the lymphocytes ability to bind. In contrast, readding antigen to cultures during incubation prevents the predicted dissociation. Moreover, repulsing M∅ cultured without selected PEL restores their capacity to bind fresh selected PEL. These findings indicate that decay of antigen associated with M∅ is the major mechanism underlying the observed dissociation.