T-Cell-Replacing Factor and Its Acceptor Site on B Cells: Molecular Properties and Immunogenetic Aspects

It has been generally postulated that B-cell proliferation and differentiation into immunoglobulin (Ig)-producing cells are regulated by several soluble factors derived from macrophages and T cells. This has been demonstrated in both antigen-specific responses (Dutton et al., 1971;Schimpl and Wecker, 1972; Hamaoka et al., 1973; Harwell et al., 1976, 1980; Delovitch and McDevitt, 1977; Takatsu et al., 1980b; Andersson and Melchers, 1981; Takatsu and Hamaoka, 1982; Swain et al., 1982; Howard et al., 1982) and nonspecific responses induced by anti-Ig as a stimulator analogous to the antigen (Kishimoto and Ishizaka, 1975; Parker et al., 1979; Pure et al., 1981;Isakson et al., 1982; Yoshizaki et al., 1982; Nakanishi et al., 1983). However, the biochemical identification and characterization of such soluble factors and the determination of a cascade reaction of those factors in B-cell proliferation and differentiation have been difficult due to the mixture of activities closely related in those functions. One approach to solving this problem has been to use soluble products from monoclonal T-cell hybridomas, which release selected lymphokine activity.