Functional roles of phenylalanine(7) of thymic humoral factor-gamma 2 in the impaired blastogenic response of uremic T-lymphocytes.

ABSTRACT

The peptide analogs of thymic humoral factor-gamma 2 (THF-gamma 2) in which phenylalanine residue at the 7th position are replaced by phenylglycine (Phg), homophenylalanine (Hph), and 1-naphthylalanine (1-Nal) were synthesized by a solid-phase method and the immunological significance of the aromatic amino acid of this position was comparatively investigated. The in vitro restoring effect of the synthetic peptides on the impaired phytohemagglutinin (PHA) response of T-lymphocytes from uremic patients was tested. The observed activities of these peptides were in order (1-Nal7) thymic humoral factor [THF]-gamma 2 > 4-Fluoro (Phe7) THF-gamma 2 > THF-gamma 2. However, the other two analogs, [Phg7] THF-gamma 2 and [Hph7] THF-gamma 2, had no restoring effect even at a higher concentration.