A heterogeneity of the HD-receptor, demonstrable by HD-cold antibodies: HD1-HD2-immunochemical aspects.

The HD receptors of human erythrocytes, which are demonstrable by HD cold auto antibodies and can be inactivated by both neuraminidase and proteases, are heterogenous. Whereas the HD1 receptor was found exclusively on human erythrocytes, the HD2 receptor could be demonstrated on human as well as on rat and guinea-pig erythrocytes. As neuraminidase has been shown to be the ‘specific’ enzyme for inactivating both the HD1 and HD2 receptors it can be concluded that also the configuration of the neuraminic acid as the HD determinant must be different. The special position of the HD receptor complex in comparison to other receptors determined by neuraminic acid is stressed.