Distribution of 'free' and HLA-associated human beta 2-microglobulin in some plasma membranes and biological fluids.

The distribution of free and HLA-associated human beta 2-microglobulin (beta 2m) in serum, urine, spinal fluid, parotid duct saliva, seminal fluid, amniotic fluid and whey and in membranes from thrombocytes, lymphocytes, neutrophils and fat globules from milk was studied by crossed radioimmunoelectrophoresis (CRIE). The hydrophobic domain of HLA was demonstrable in 'charge-shift CRIE' and by binding to phenyl-Sepharose in 'hydrophobic-interaction CRIE'. In 'lectin-affinity CRIE' with concanavalin A and Lens culinaris lectin Sepharose the carbohydrate moiety present on. HLA exhibited heterogeneity as judged by the appearance of two partly separated protein peaks. Except for isolated fat globule membranes, HLA-associated beta 2m was present on all cells investigated. 'Free' beta 2m did not contain a hydrophobic domain as assessed by charge-shift and hydrophobic-interaction CRIE. All body fluids contained beta 2m in its 'free' form only. In serum, besides the free beta 2m, 2% was present as HLA-associated beta 2m, which, however, did not contain a hydrophobic domain. A degradation product of 'free' beta 2m, with alpha-mobility, was observed in sera from patients with malignant disorders, rheumatoid arthritis or systemic lupus erythematosus.