Immunochemical relationships between bacteria belonging to two separate families: pneumococci and Klebsiella.

The cross-reactions of more than 60 capsular (K) type-specific polysaccharides of Klr~hsiellu in antipneumococcal sera of 26 specific types and in several anti-Salr~~o/iellu sera are described and discussed, many for the first time. Quantitative data on the extent of cross-reactivity are given in many instances. From these, and from a study of residual fractions of antibody in the supernatants, it has been possible to confirm the presence of non-reducing end-groups of wglucuronic acid in KZ. K8 and KZO. Such groups were also correctly predicted for K9 and K59 and will most probably be found upon chemical examination of K15, K23, K27, K30, K33, K45. K51 and K55. Non-reducine end-groups of L-rhamnose were correctly predicted for K47 and K56 and will likewise be found in K17 and K19. Other correlations of chemical structure and immunological specificity are pointed out, as well as limitations of the methods used.