Serum haptoglobin suppresses T-lymphocyte functions following burns

It is well known that serum immunosuppressive factors play an important role in the mechanism of postburn immunosuppression. This study was intended to investigate the effect of haptoglobin, purified from the serum of burned patients by affinity chromatography, on the proliferation and interleukin-2 (IL-2) secretion of normal murine thymocytes induced by ConA and the proliferation of IL-2 dependent cell line (CTLL-2) stimulated by recombinant human IL-2, so as to elucidate the role of serum haptoglobin in postburn T-lymphocyte dysfunction. The results showed that purified haptoglobin, at the level equivalent to the concentration found in serum of burned patients, significantly inhibited the proliferation and IL-2 secretion of normal murine thymocytes as well as CTLL-2 proliferation; whereas it exhibited no immunosuppressive effects at the level equivalent to the concentration found in serum of normal volunteers. According to the results reported here, it is suggested that extraordinary increase in serum haptoglobin level may be an important factor of impaired T-lymphocyte responses following burns.