Primary in Vitro Antibody Response of Human Peripheral Blood Lymphocytes: Role of Phagocytic Mononuclear Cells

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Abstract
We have studied the role of monocytes in the primary in vitro antibody response induced by the insolubilized conjugate of the hapten trinitrophenyl to polyacrylamide beads (TNP-PAA) in cultures of human peripheral blood lymphomonocytic cells (PBL). The depletion of adherent cells by passage on Sephadex G-10 columns does not modify the response. The functional elimination of phagocytic cells by the addition of silica is able, at the higher concentration used (1 mg/culture), to suppress the response profoundly. This response can be restored by the addition of 2-mercaptoethanol (2-ME). The lower concentration of silica (100 µg/ml) has an inconstantly suppressive effect, which, when present, is as marked as that of 1 mg/culture. One hundred micrograms of silica alone are able to stimulate the response in some cases, and when associated with 2-ME, has a reproducible enhancing effect. The addition of silica to the PBL of one of the few nonresponders to TNP-PAA allows a response from these cells. Silica does not allow the response of T-depleted cells to TNP-PAA. Thus, monocytes play a role in the response of human B cells to TNP-PAA, with two contrasting effects: Their presence is necessary in order to obtain a response, and in this respect they can apparently be replaced by 2-ME. They have an inhibitory effect which may, in rare instances lead to the absence of an in vitro response.