INFLUENCE OF ANTICOAGULANTS ON THE LEVEL OF SOLUBLE HLA CLASS-I AND CLASS-II ANTIGENS MEASURED IN BLOOD-SAMPLES

The existence of soluble forms of HLA class I and class II antigens in human serum is well established and altered concentrations of these s erum proteins have been described to be associated with various diseas es. Since soluble HLA antigens (sHLA) can be measured both in serum an d plasma samples, we investigated whether anticoagulant treatment infl uences the determined levels of soluble HLA class I (sHLA-I) or solubl e HLA-DR (sHLA-DR). Analyzing paired samples of serum and plasma of 40 healthy individuals we found significantly lower serum levels of sHLA -DR (0.31 +/- 0.15 ng/ml) compared to EDTA plasma levels (0.58 +/- 0.2 0 ng/ml). By contrast, serum levels of sHLA-I (0.89 +/- 0.74 mu g/ml) were only slightly lower than EDTA plasma values (0.95 +/- 0.86 mu g/m l), a situation similar to that of sIL-2R and sCD4 levels. Further exp eriments intended to clarify the reasons of the reduced sHLA-DR serum levels revealed that (i) the blood storage time before centrifugation did not influence the sHLA-DR level, (ii) treatment of serum with anti coagulant did not augment the measured sHLA-DR concentration, and (iii ) the recovery of spiked sHLA-DR was significantly lower when added to native blood than to serum or anticoagulant-treated blood. These resu lts suggest that sHLA-DR is partly removed by the process of blood clo tting thus resulting in diminished sHLA-DR serum levels.