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Suppression of an in vitro humoral immune response by cultured fetal thymus cells
We studied the function of fetal thymocytes, derived from thymus progenitor cells of 14-day-old fetuses in an organ culture system, in an in vitro humoral immune response. The unprimed cultured fetal thymocytes suppressed the T-dependent primary immune response to adult syngeneic spleen cells against sheep red blood cells, but failed to suppress the response against the T-independent antigen NIP-POL [4(hydroxy-3-iodo-5-nitrophenyl)acetyl-coupled polymerized flagellin]. The suppression was abolished by anti-Thy-1 serum and complement treatment. Using a differential killing procedure, the suppressor cells were characterized as "low" Thy-1 cells. In addition, they were resistant to hydrocortisone. Suppression could only be achieved when the cultured fetal thymocytes were added during the first 48 h of culture, suggesting that their action occurred during the induction phase of the response. The implications of the high frequency of suppressor cells during fetal life are discussed.
We studied the function of fetal thymocytes, derived from thymus progenitor cells of 14-day-old fetuses in an organ culture system, in an in vitro humoral immune response. The unprimed cultured fetal thymocytes suppressed the T-dependent primary immune response to adult syngeneic spleen cells against sheep red blood cells, but failed to suppress the response against the T-independent antigen NIP-POL [4(hydroxy-3-iodo-5-nitrophenyl)acetyl-coupled polymerized flagellin]. The suppression was abolished by anti-Thy-1 serum and complement treatment. Using a differential killing procedure, the suppressor cells were characterized as "low" Thy-1 cells. In addition, they were resistant to hydrocortisone. Suppression could only be achieved when the cultured fetal thymocytes were added during the first 48 h of culture, suggesting that their action occurred during the induction phase of the response. The implications of the high frequency of suppressor cells during fetal life are discussed.