Serological cross-reactions of leptospiral lipopolysaccharide (F4) antigen.

: The serological specificity of leptospiral lipopolysaccharide (F4) antigen was examined by the technique of passive haemagglutination. F4 extracted from leptospiral serovars representative of several different serogroups showed wide cross reaction between serovars, including numerous one-way (non-reciprocal) reactions. The pattern of cross reaction was different to that of the standard leptospiral classification scheme.