The effects of fractions (chalones) obtained from lymphoid organs on the immune response in vivo.

Aqueous extracts of calf and pig lymphoid organs were prepared and fractionated by means of gel filtration, ion exchange chromatography, and isoelectric focusing. These fractions, which had been previously assessed on mitogen-stimulated mouse spleen lymphocytes and other cells in vitro, were tested for their in vivo activity on humoral (haemolytic PFC in mice) and on cell-mediated immunity (skin allograft survival in mice, lymph node weight assay in rats, and systemic GvH-reaction in mice). None of these several fractions elicited either biologically significant or reproducible inhibitory effects. In particular, two fractions, a high and a small molecular weight fraction which were strongly inhibitory in vitro, remained without any chalone-like activity in these in vivo assays. Our results therefore failed to support the existence of a lymphocyte chalone.