Surface receptors and immune activity of purified human circulating mononuclear cells. V. Circulating null cells and a factor secreted by the null cells inhibit the synthesis of receptors for Fc mu by T cells in culture.
Receptors for Fc mu (Fc mu R) were not detected on freshly isolated unfractionated circulating human mononuclear cells (MNC) or purified T cells. However, a significant percentage of the T cells (20% to 40%), but not of the unfractionated MNC, exhibited Fc mu receptors following culture for 24 h at 37 degrees C in medium enriched with fetal calf serum. These receptors were newly synthesized by the T cells since they were not detected on T cells cultured for 24 h with cycloheximide in a non-cytotoxic concentration. The absence of Fc mu R on the cultured unfractionated MNC (of which 70% are T cells) suggested that non-T cells within the MNC-B cells and/or null cells and/or monocytes suppressed the synthesis of Fc mu R by the T cells. These cells were individually assayed for their capacity to suppress Fc mu R synthesis by co-cultured T cells. The null cells were able to totally suppress Fc mu R synthesis whereas the B cells and monocytes exhibited no suppressive activity. Null cells cultured for 24 h at 37 degrees C secreted a factor which inhibited the synthesis of receptors for Fc mu by the cultured T cells. This factor is referred to as receptor synthesis suppressor factor or RSSF. On the basis of these findings, it is concluded that (a) the circulating T cells do not possess Fc mu R; these receptors are synthesized de novo by the T cells in culture, (b) the null cells, but neither the B cells nor the monocytes, suppress the synthesis of the Fc mu R by the T cells and (c) the null cells, but neither the B cells nor the monocytes, secrete a factor, receptor synthesis suppressor factor, which can suppress the synthesis of Fc mu R by the T cells.
Richter
M
M
Department of Pathology, Faculty of Medicine, University of Ottawa, Ontario, Canada.
Kamran
M
M
Jodouin
C A
CA
D002478:Cells, Cultured; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000502:physiology; D008215:Lymphocytes, Null / Q000502:physiology*; D011961:Receptors, Fc / Q000096:biosynthesis*; D013491:Suppressor Factors, Immunologic / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism*
D007075:Immunoglobulin M; D011961:Receptors, Fc; D013491:Suppressor Factors, Immunologic; C035311:immunoglobulin M receptor