Antigenic specificity and cellular mechanisms in leukocyte adherence inhibition analysis of immunity to simple proteins and hapten-protein conjugates.

The hemacytometer leukocyte adherence inhibition (LAI) assay was investigated with respect to immunological relevance, specificity, and cellular mechanisms. Humans were immunized to keyhole limpet hemocyanin, and rats were immunized to dinitrophenyl-bovine gamma-globulin. LAI analysis disclosed classic patterns of immune response kinetics. The LAI response was dose dependent in vitro with no inhibition at relatively high antigen doses. In vitro specificity in rats was restricted to the immunizing conjugate. Cells forming spontaneous E-rosettes were required for LAI reactions. Lymphokine production required the presence of E-rosette-forming cells. E-rosette-forming cells from normal donors lost adherence in the presence of lymphokine. The requirement for T-lymphocytes was confirmed in a human osteosarcoma system using independent criteria. Thus, the hemacytometer LAI depends upon T-lymphocyte collaboration via a lymphokine. It should be distinguished from the tube and microplate variants of LAI analysis because these appear to depend upon different mechanisms.