| Abstract: | ![]()
A non-complement fixing monoclonal antibody (Q2/70) to framework determinants of human Ia-like antigens was used to develop a method for isolating Ia-like antigen bearing, i.e., Ia-like (+) cells and cells lacking these antigens, i.e. Ia-like (?), from human peripheral blood lymphocytes (PBL). The method was based on sensitization of PBL with the antibody Q2/70, followed by rosetting with sheep (ShE) coated with purified rabbit anti-mouse Ig antibodies, differential centrifugation on a Ficoll-Hypaque gradient, and finally recovery of Ia-like (+) and Ia-like (?) cells from the bottom and the interface of the gradient respectively. Marker analysis of the two cell subpopulations showed that the majority of the bottom cell fraction were Ia-like (+) and carried B cell markers such as membrane bound immunoglobulins (MbIg) and C3 receptors. On the other hand, the majority of the interface cell fraction were Ia-like (?) and carried T cell markers such as receptors for 2-aminoethylisothiouronium treated sheep erythrocytes (AETShE) and goat erythrocytes (GoE). Serological and functional studies showed that the Ia-like (+) cells (1) were useful targets in complement mediated cytotoxicity assays for HLA-DR typing; (2) served as stimulator but not as responder in unidirectional mixed lymphocyte reactions (MLRs); (3) did not display lytic activity in natural killer (NK) cell cytotoxicity and in antibody dependent cellular cytotoxicity (ADCC); and (4) proliferated in response to pokeweed mitogen (PWM) stimulation in the presence of helper T cells. On the other hand, the Ia-like (?) cells (1) responded to but failed to stimulate allogeneic lymphocytes in the MLRs; (2) were highly active in NK and ADCC assays; and (3) provided helper activity in PWM stimulation of purified B cells. |
