Therapeutic immunoadsorption increases the level of circulating soluble HLA molecules

Immunoadsorption (IA) is an established procedure to remove Igs and immune complexes from peripheral blood. Since Igs reportedly bind to human leucocyte antigen (HLA) molecules, we were interested to know whether removal of Ig will also influence the plasma concentration of soluble HLA (sHLA).

Nine patients suffering from severe autoimmune disease and undergoing 17 single courses of IA treatment were monitored for their sHLA class I (sHLA-I) and sHLA-DR plasma levels. Plasma was separated by a hollow-fiber-type separator. Plasma samples were taken before therapy, after 15 min of recirculation (without operating the adsorber), after 1 and 2 liters of plasma adsorption, and 24 and 48 h after the end of IA.

Before treatment the mean levels of sHLA-I and sHLA-DR were 0.37 (+/-0.06 SEM) and 0. 32+/-0.05 microg/ml, respectively. After 2 liters of plasma filtration, an increase in sHLA-DR (0.80+/-0.10 microg/ml) was observed (p<0.001), whereas sHLA-I was only slightly affected (mean: 0.45+/-0.06 microg/ml). sHLA concentrations returned to initial levels after 24 h.

The significant increase in sHLA-DR may contribute to the immunomodulatory effect of IA.