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Bone marrow macrophages induced to antigen presentation by lymphokines interact selectively with distinct T cells

In vitro matured bone marrow‐derived macrophages (BMMϕ), which represent a pure population of Mϕ, were shown to act as antigen‐presenting cells (APC) to the T cell clone ST2/K.9. This interaction was major histocompatibility complex restricted. Upon long‐term culture in macrophage colony‐stimulating factor, BMMϕ were activated for antigen presentation by a 48‐h pulse with lymphokine‐containing supernatant of concanavalin A‐stimulated rat spleen cells (Con A sup). The capacity of such activated Mϕ to function as APC decreased upon removal of Con A sup, and could be regenerated by a second pulse. This finding suggests that antigen presentation by mature Mϕ is a reversible function regulated by T cell factors. When the responsiveness of various T cell lines to antigen presented on BMMϕ or spleen cells was compared, distinct activation requirements were observed for different T cells since lymphokine‐activated BMMϕ were not capable of inducing antigen‐specific proliferation of all lines.