REGULATION OF HAPTEN-SPECIFIC MEMORY IGE RESPONSES INDUCED IN-VITRO -REQUIREMENT FOR BOTH THY-1-1+ ASGM1- CELLS AND FOR IFN-ALPHA AND IL-4( ASGM1+ AND THY)

The roles of Thy-1+ and AsGM1+ spleen cells and cytokines (IL-4, IL-5, IL-6, IFN-alpha, and IFN-gamma) in regulation of hapten-specific memo ry IgE antibody-forming cell (AFC) responses induced in vitro were exa mined. BALB/c mice, injected i.p. with benzylpenicilloyl-keyhole limpe t hemocyanin (BPO-KLH) (10 mug) on days 0 and 21, were killed on day 6 0 or day 120. Numbers of BPO-specific IgGl, IgE, and IgA AFC in spleen were determined by enzyme-linked immunosorbent spot assay after 0 to 6 days of culture +/- BPO-KLH. BPO-specific AFC of all isotypes were d etected in spleen on day 60, but not on day 120. Day 60 AFC responses did not persist in culture in that no AFC were detected by day 2 of cu lture +/- BPO-KLH. When either day 60 or day 120 cells were cultured f or 3 days with BPO-KLH, BPO-specific AFC responses were induced, and p eaked on day 5, with similar numbers of AFC of each isotype induced wi th day 60 and day 120 cells. On day 60, spleen contained two subsets o f Thy-1+ cells: AsGM1- (approximately 32% of total cells) and AsGM1+ ( approximately 4%). Depletion and reconstitution experiments establishe d that both subsets were required for induction of BPO-specific IgE AF C responses. Cytokines could not substitute for the Thy-1+-depleted ce lls. However, when unfractionated day 60 cells were cultured with cyto kines or anti-cytokine antibodies, BPO-specific IgE AFC responses indu ced were both IFN-alpha and IL-4 dependent; either increased or decrea sed by IFN-gamma, depending on its concentration, and unaffected by IL -5 or IL-6.