Peritoneal exudate lymphocytes (PEL) from immunized guinea pigs, when pulsed with antigen, rapidly release a T-cell stimulatory factor (TSF). TSF nonspecifically enhances the proliferation of purified guinea pig T cells in the presence of another signal such as PMA, PHA, or Con A. On a per cell basis, antigen-pulsed PEL produce about 14 times more activity than similarly stimulated lymph node lymphocytes. Several lines of evidence support the view that TSF is the guinea pig equivalent of TCGF (IL-2). TSF containing supernatants have IL-2 activity when assayed on the IL-2-dependent CT6 cell line. When TSF containing supernatants were absorbed with CT6 cells, there was a significant decrease of both TSF activity as assessed on guinea pig T cells as well as IL-2 activity as assessed by the CT6 assay. Additionally, partially purified human and mouse IL-2 have TSF activity, while the macrophage product, IL-1, has no TSF activity. After chromatography on a S-200 column, TSF activity and IL-2 activity coelute at an apparent molecular weight of 19,000.
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