The Mechanisms involved in the Production of Red Cell Panagglutinability by Streptococcal Cultures.

Treponemes are shown to be about twenty times as sensitive to immobilizing antibody at 35° as at 25° C., so it was conjectured that our former technique of preliminary incubation of treponema suspension and test serum merely served to accustom the treponemes to the 35° temperature in the environment. Experiment confirmed that a preliminary incubation of the suspension alone, in bulk, was an adequate substitute; thus, the technique has been simplified. Different strongly reactive sera or pools appear to act similarly, as they should if they were merely different dilutions of the same active agent. A different value from 2 may sometimes be more suitable for the slope coefficient ϒ of log t in regressions versus log D, where D is the 50 per cent immobilizing dilution; but 2 may be used as approximation for ϒ in correction factors applied to observations made at only moderately different times. Three World Health Organization TPI controlserum preparations were tested simultaneously with five of our own strongly reactive rabbit-serum pools in a series of experiments, yielding fairly reliable estimates of their relative potencies. This permitted making a blend as a replica (ALB1) for replacement of our nearly exhausted supply of the second international TPI control serum (WHO2W) that we had obtained in whole-serum form. The third international control serum (WHO3) was shown to have about 73 per cent of the potency of the WHO2W control serum, whose potency we had taken as standard, p_°= 100. It was shown that WHO3, which is composed of human serum, is similar in action to rabbit serum pools; hence the latter appear adequate for use as standards of reference in testing human sera. [ABSTRACT FROM AUTHOR]