EFFECTS OF HUMAN CALPROTECTIN (L1) ON IN-VITRO IMMUNOGLOBULIN-SYNTHESIS

Calprotectin (L1) is a major cytoplasmic protein of neutrophilic granu locytes and monocytes/macrophages which is released from leucocytes du ring activation or cell death. Apart from in vitro antimicrobial and a ntiproliferative activity little is known about the biological functio n of the protein. Since previous investigations have shown that calpro tectin plasma levels are elevated in various inflammatory rheumatic di seases, we wanted to investigate if calprotectin has an effect on immu ne cell functions. Peripheral blood mononuclear cells, either unstimul ated or polyclonally stimulated with mitogen, were incubated with calp rotectin and effects were assessed by enumeration of immunoglobulin se creting cells (ELISPOT). The results indicate that incubation with hig h concentrations of calprotectin (>64 mu g/ml) inhibit the production of the three classes of immunoglobulins investigated (IgG, IgM and IgA ), both for mitogen stimulated and unstimulated lymphocytes. Except fo r the highest concentration of calprotectin (500 mu g/ml), it seems pl ausible that the observed inhibitory effect of calprotectin on Ig prod uction is not a result of a direct toxic effect of calprotectin on B l ymphocytes. Altogether, these effects of high calprotectin levels migh t be of importance in the immunoregulation of inflammatory conditions.