Serum amyloid A (SAA) is a major acute-phase protein whose biochemical functions remain largely obscure. Human rheumatic synovial fluids were screened by high performance liquid chromatography mass spectrometry for SAA-derived peptides, specifically the sequence AGLPEKY (SAA 98À104 ) which was previously shown to modulate various leukocyte functions. Two such fluids were found to contain a truncated version of SAA 98À104 . Synthetic SAA 98À104 and several of its analogs were shown capable of binding isolated human CD + 4 T-lymphocytes and stimulating them to produce interferon-Q Q. Given the high acute-phase serum level of SAA and its massive proteolysis by inflammatory related enzymes, SAA-derived peptides may be involved in host defense mechanisms.z 2000 Federation of European Biochemical Societies.

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When deprived of serum, oligodendroglialike (OLN 93) cells grown on poly-L-lysine-coated culture dishes cease to proliferate after 3 days and morphologically extend many fibers resembling morphologically differentiated, immature oligodendrocytes. At this time no cell death is apparent unless serum deprivation is extended for a period longer than 1 week. After 3 days in serum-deprived medium, treatment of cells with 1 mM H2O2 for 30 min facilitates apoptotic cell death, even when serum is added during the recovery period. Both serum-deprived, differentiated cells, and proliferating cells, respond to H2O2 by an initial growth arrest followed by growth resumption after 48 hr. However proliferating cells show resistance to the apoptotic effect of H2O2. This is correlated with growth arrest in the S phase at different stages of DNA replication, as well as with different timing of induced p21Waf1 expression. Thus, cells grown in serum, express elevated p21Waf1 protein levels after 4 hr, whereas serum-deprived, differentiated cells, only after 24 hr. The mRNA levels of p21Waf1 follow a similar timed pattern. Hence p21Waf1 may protect OLN 93 cells against the genotoxic effect of H2O2. The data suggest an intimate relationship between G1-arrest, morphological differentiation, and H2O2-mediated apoptosis.

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