title: Presence of thymosin-like factors in human thymic epithelium conditioned medium.
abstract: The objective of the present study was to determine whether or not thymosin and conditioned medium from human thymus epithelial cultures (HTECM) contain similar fractions, capable of inducing T-cell differentiation. Therefore we tested the ability of rabbit antisera to different thymosin fractions (thymosin fractions 5, 6 and alpha 1) of both bovine and human origin to block the stimulatory effect of HTECM on Con A and PHA response of mouse thymocytes. We also looked for reactivity of the antisera toward tissues of man, mouse and calf, and to tissue cultures of man and mouse. Anti-thymosin fraction 5 and 6, but not anti-thymosin-alpha 1, were found to inhibit the stimulatory effect of HTECM on both Con A and PHA responses. This cannot be attributed to cytostatic or cytotoxic effects of the antisera on thymocytes. No effect was seen when using antiserum to kidney fraction 5 or normal rabbit serum. In both tissue sections and tissue cultures of the different species tested, anti-thymosin reacts only with thymus epithelial cells. The reactivity is blocked by neutralizing the antisera with thymosin fraction 5 but not by kidney fraction 5. The reactivity is also strongly diminished by neutralizing the antisera with HTECM but not with supernatants of conditioned media from non-thymic tissues. The observations are highly suggestive for the presence of similar fractions in HTECM and thymosin, and that both are secreted by thymus epithelial cells.
mesh_terms: D000818:Animals; D000906:Antibodies; D002417:Cattle; D003470:Culture Media; D046508:Culture Techniques; D004848:Epithelium / Q000032:analysis; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D011817:Rabbits; D013601:T-Lymphocytes / Q000276:immunology; D013947:Thymosin / Q000032:analysis* / Q000276:immunology; D013950:Thymus Gland / Q000032:analysis* / Q000276:immunology; D013951:Thymus Hormones / Q000032:analysis*
chemical_list: D000906:Antibodies; D003470:Culture Media; D013951:Thymus Hormones; D013947:Thymosin