Dissociation in Pasteurella pestis: immunological comparisons of smooth and non-smooth variants.

Altlhough the literature on the immunology of Pasteurella pestis is extensive, relatively little attention has been given to the immunological specificity of colonial variants. This may have been due to difficulties encountered in the propagation of pure nonsmooth variants, and for this very reason their serological specificity might be considered to be of minor importance; colonial morphology being dependent to some extent upon environmental factors for expression (Otten, 1936; Jawetz, 1940). Until recently, serological techniques of sufficient delicacy to detect antigenic differences between smooth and nonsmooth variants have been lacking. There has also been some confusion in applying the terms smooth and nonsmooth or rough, some workers designating antigenic differences and others applying the distinction only to morphology. Pirie (1929) separated morphologically distinguishable normal smooth and variant rough forms of P. pestis which differed in their biochemical, serological, and immunological characteristics. The nonvirulent rough form was ineffective as an immunizing agent in rats and guinea pigs. Rabbit antiserum prepared with this form was useless therapeutically. Schiutze (1932) found P. pestis to consist of two antigens: rough organisms consisting of rough soma only, and smooth cells containing an additional antigen, the envelope substance. The latter induced greater protection in guinea pigs (Schiltze, 1939) and a higher anti-envelope titer in rabbits. Schuttze could not distinguish