An evaluation of the existence of soluble suppressor factors in cloned antigen-specific T suppressor lymphocytes.

The suppressive activity of two bovine serum albumin-specific class II-restricted T suppressor cell clones (BVI/5 and 83/2-D11) was compared to that of a feeder cell-independent, IL 2-dependent subline (HF1.IL-2) of an originally antigen-dependent class II-restricted Ts cell clone (HF1). No soluble suppressor factors can be found in BVI/5 and 83/2-D11 Ts cell extracts or culture supernatants under conditions where an unspecific factor can be derived from HF1.IL-2 cells. This factor, when isolated from cell extracts in the presence of n-octyl-beta-D-glycopyranoside, has a molecular weight of 70-80 kD. In absence of this non-ionic detergent, it has a high affinity to membrane fragments and is associated with a molecular weight of 300 kD or more. The data are discussed in connection with recent findings of direct T suppressor to T helper interaction by cell-cell contact.