The role of the Fc receptor (FcR) of thymus‐derived lymphocytes II. Presence of FcR on suppressor cells and direct involvement in suppression

Abstract

The role of the Fc receptor (FcR) of thymus-derived I y m phocytes Presence of FcR on suppressor cells and direct involvement in suppression*Alloantigen-activated T cells (ATC) were prepared by injecting C3H/He thymocytes into host-irradiated BALB/c mice. ATC were taken from the spleen of the recipients at day 5 and tested for their activity o n "in vitro" primary antibody production t o sheep red blood cells (SRBC) induced in splenic C3H/He lymphocytes. ATC added 24 h after antigen were found t o be suppressive. Separation of ATC by velocity sedimentation, according t o cell size showed that suppressor cells were found in each population, medium and large lymphocytes, however, being more active. Separation of ATC, according t o the presence of Fc receptor (FcR) at their membrane was achieved by velocity sedimentation after rosetting with IgG-sensitized SRBC (EA). Suppressor cells were then found in FcR+ and not in FcR-fractions, the degree of suppression being parallel t o the ratio of FcR+ cells. At both extremes, pure populations of FcR+ cells were highly suppressive, while populations of ATC, completely devoid of FcR' cells, were inactive. Since FcR is a very labile molecule a t the T cell surface and shed within 3 h at 37 "C, but not at 4 "C, ATC were pre-incubated at each temperature and added 24 h after antigen t o the spleen cell cultures. In these cases, ATC having released their FcR, were much less suppressive than control ATC, and in previous work we have shown that the suppressive activity was found in the cell supernatant associated with an FcR-like molecule (immunoglobulin-binding factor). The data therefore allow the conclusion that FcR may be a marker of nonantigen-specific suppressor T cells and seems t o be involved itself in the suppression phenomenon.

Localization of human antigen-specific helper and suppressor function in distinct T-cell subpopulations

“…In mice as well as in man it has been shown that T-cells release FcyR which exert nonspecific suppression of the primary PFC response to SE in vitro (19,20). The cells were found to be less suppressive after having lost their FcR (19).…”

“…In mice as well as in man it has been shown that T-cells release FcyR which exert nonspecific suppression of the primary PFC response to SE in vitro (19,20). The cells were found to be less suppressive after having lost their FcR (19). Cordier et al (21) reported that the FcyR is irreversibly lost by human T-cells after interaction with insoluble immune complexes.…”

Regulation of B Cell Activity in Man: Role of T Cells

“…It has been reported that FcyR released by (activated) T cells suppress nonspecifically a primary PFC response to SE in vitro (Fridman et al 1977, Molenaar et al 1977. The finding that antigen-20 RUDY E. BALLIEUX' \ COBI J. HEIJNHN'.…”

T cell‐produced immunoglobulin binding factor (IBF) bears determinants coded for by the I region of the major histocompatibility complex and lacks allogeneic restriction

“…IBF is produced by cortisone-resistant thymocytes [25] and by GVH-activated spleen T cells [25]. Whithin this cell population, IBF is produced by Fc receptor (FcR)-positive T cells [26], which themselves act as nonantigen-specific suppressors of in vitro antibody production [27]. IBF may, therefore, be the soluble form of the T cell FcR and the mediator of the suppression exerted by the FcR-positive activated T cells.…”

“…This hypothesis is strengthened by the fact that (a) IBF is only produced by FcR-positive T cells or FcR-positive T cell lines both in the mouse [26,281 and in man [29, 301; (b) IBF is produced at 37 "C in conditions where FcR is released from the T cell surface [26]. Incubation in the cold or in the presence of protein synthesis inhibitors, which blocks FcR release, inhibits IBF production [26]; (c) finally, activated T cells partially loose their suppressive activity after releasing their FcR, and this activity is found to be associated to IBF in the supernatant [27].…”