Purification and partial amino acid sequence of suppressive lymphokine from a CD8+ CD57+ human T hybridoma.

A T-suppressor (TS) lymphokine was purified from the supernatant of a T hybridoma established from CD3+ CD8+ CD57+ lymphocytes of a healthy bone marrow transplant patient. Using polyclonal rabbit antibodies, raised against a TS-enriched preparation, a specific protein of 47,000 MW was identified, which was used to prepare monoclonal antibodies. The screening of hybridomas was carried out by strip-ELISA, in which the 47,000 MW band, transferred on a membrane, served as antigen. One of these monoclonal antibodies (IgM kappa) was selected for purification of the native TS molecule, which exhibited the high suppressive activity on the phytohaemagglutinin (PHA) and alloantigen responses of peripheral blood lymphocytes. The establishment of amino acid sequences of five trypsinized cleavage peptides confirmed that this protein has not been previously identified. This lymphokine--also detected in the supernatant of normal CD8+ CD57+ lymphocytes--is likely involved in bone marrow transplantation tolerance.