The regulatory effect of histamine on the immune response: characterization of the cells involved

Any immunological response is the end result of the equilibrium between many positive and negative regulatory factors. It has been recently demonstrated that histamine receptor-bearing T lymphocytes could play a role in this regulation. This work aims to study the effects of different cell populations after incubation with histamine on the proliferative response of normal lymphocytes. The histamine-incubated peripheral blood lymphocytes (PBL) lower the proliferative response of normal cells toward mitogens (phytohemagglutinin, concanavalin A) and antigens (mixed lymphocyte culture). In order to precise the cell subpopulations involved in this suppression, PBL have been depleted of adherent cells and B and T lymphocytes have been purified by a standard rosette technique. The enriched B cells do not suppress the normal response but the suppressor activity of T cells, as well as adherent cell-depleted PBL, are significantly reduced compared to the one of PBL. The initial suppressor activity is restored by addition of 1% adherent cells (and not 5 or 10%) to adherent cell-depleted lymphocytes and 10% adherent cells (not 1 or 5%) to T-enriched population. These observations suggest a role for adherent cells in this regulation.