Dysfunction of thymocytes of C3H/HeJ mice in blastogenic response to anti-thymocyte serum in vitro and its repair with lipopolysaccharide induced mediator.

In vitro mitogenic responses of thymocytes to rabbit anti-mouse thymocyte serum (ATS) have been compared in several mouse strains. The response of thymocytes of C3H/HeJ mice is about one-third of those of thymocytes of C3H/He, ATL or ATH strains. Phenol-extracted bacterial lipopolysaccharide (LPS) does not induce mitogenic response in cultured C3H/HeJ spleen cells, but the spleen cells of all other strains used are capable of responding to LPS. The low response of C3H/HeJ thymocytes to ATS is restored by adding “endotoxin soup” prepared from spleen cell cultures of LPS-responder mice in the presence of LPS. Neither soup prepared from C3H/HeJ spleen cell cultures without the addition of LPS nor soup prepared from cell cultures with LPS show such restoration of the response of C3H/HeJ thymocytes to ATS. The molecular size of the active factor in “endotoxin soup” was estimated on a Sepharose CL-4B column and determined to be about 20,000 daltons. The activity of “endotoxin soup” is destroyed by heating at 70 C for 30 min or 80 C for 10 min and diminished by digestion with trypsin. The mechanisms of restoration of low response of C3H/HeJ thymocytes to ATS by “endotoxin soup” are discussed.