New Insight into Lymphocytic Chalone Research

Abstract
Immunosuppressive activities have been detected in bovine spleen extracts and attributed to the presence of a ‘lymphocytic chalone’. Following the immunosuppression of a T cell-dependent humoral response in mice as assay, we purified a peptide to homogeneity present at a concentration of 10–50 ng/kg of spleen whose properties were identical to those of the serum thymic factor. This factor appeared to be a regulator of the humoral immune response in the splenic extract and as such might be responsible for part of the immunosuppressive activities detected in the splenic ‘chalone’ fraction.