HLA in human serum--quantitation of class I by enzyme immunoassay.

A solid-phase, enzyme-linked immunoassay was used to quantitate the soluble fraction of HLA-class I. The sera of 318 individuals were studied, as well as the urine of six individuals with normal renal function. The stability of blood concentrations of the soluble HLA was also evaluated. The data justify the following six conclusions. (1) All normal people have circulating HLA (mean = 357 ng/ml). (2) The population can be divided into one group of low secretors (mean = 162.4 +/- 65.2 ng/ml) and another group of high secretors (mean = 540.7 +/- 185.9 ng/ml) (P less than 0.01). (3) Blood levels in each individual are reasonably consistent over short (days) and long (years) periods of time. (4) The mean concentration of soluble HLA-class I in all renal failure patients was 590 ng/ml, significantly higher than normal (P = less than 0.05); it was highest in patients on peritoneal dialysis (mean = 683 ng/ml) in spite of substantial chronic loss in peritoneal dialysate. (5) Renal allograft recipients with stable allograft function also had mean values greater than normal at 554 ng/ml (P less than 0.05). (6) Soluble HLA-class I was not detected in the urine of individuals with normal renal function.