A high Mr factor in human blood which confers serum resistance on gonococci: some properties and synergism with CMP-NANA

A high relative molecular mass (Mr) component which confers serum resistance on gonococci has been purified about 300-fold from a dialysed sonicate of human blood cells. Serum resistance conferred by the high Mr factor (RIF), like that induced by cytidine-5′ monophospho-N acetyl neuraminic acid (CMP-NANA), decreased when gonococci were incubated with neuraminidase. Also, the resistance-inducing activities of both high Mr RIF and CMP-NANA were inhibited by CMP and inactivated at pH 4.0. These activities were not additive but synergistic. Neuraminidase decreased the activity of high Mr RIF but not CMP-NANA.