Monocytes as accessory cells in the human mixed lymphocyte response: Lack of requirement at high cell densities

One-way mixed lymphocyte responses (MLR) were observed in microtiter plates with round-bottomed, but not flat-bottomed, wells between human peripheral blood mononuclear cell populations depleted of monocytes. The response in flat-bottomed wells was reconstituted when either responder or stimulator monocytes were added or when the cell density was increased. Possible implications of these results concerning the monocyte requirements for generating an MLR are discussed.