Variable region (Fv) determinants on mouse lymphocytes.

Antisera have been raised to the Fv fragment derived from a mouse alpha/lambda myeloma. These had different reactivities for Fv and mouse immunoglobulin and two of them appeared to detect v region framework determinants on normal mouse immunoglobulins. A large proportion of mouse lymphocytes were shown to have Fv determinants on the surface which was part of the B-lymphocyte antigen receptor. Most of the reacting cells were B lymphocytes. Fv determinants were not detected on the majority of T lymphocytes including cells with known T-helper cell activity. It is concluded that in mice, T cells do not express immunoglobulin v region framework determinants on their surface.