THE REQUIREMENT OF Ia POSITIVE MACROPHAGES IN THE PRIMARY IN-VITRO HUMORAL RESPONSE

Adherent splenic macrophages contain a subpopulation which expresses an Ia determinant. This Ia positive accessory cell is required for the development of a primary in-vitro antibody response to a T cell dependent antigen by murine lymphoid cells. Genes controlling Ia antigen(s) on this subset of functional macrophages map to the I-J and I-E subregions. Antibodies specific for the I-J subregion determinant (s) are also capable of blocking the function of macrophages in the in-vitro humoral response.