Human protein HC (alpha 1-microglobulin) and inter-alpha-trypsin inhibitor in connective tissue.

The presence of protein HC (alpha 1-microglobulin) and inter-alpha-trypsin inhibitor was investigated in different human tissues. Inter-alpha-trypsin inhibitor is a complex protein composed of bikunin and two heavy polypeptide chains. Protein HC and bikunin are transcribed from a common gene. Inter-alpha-trypsin inhibitor immunoreactivity was detected in mast cells. The positive reaction could be blocked by antisera absorption with bikunin, indicating that mast cells contain only bikunin. Protein HC immunoreactivity was revealed on elastic fibres in connective tissue of skin, colon and lung, and on the internal elastic lamina of blood vessels. In the testis, the basement membrane of the seminiferous tubules reacted positively with protein HC antibodies.