Abstract
The serum of the domestic fowl has been found to protect mice and guinea pigs against infection with the pneumococcus. The protective power of the serum was demonstrated by giving mice, intraperitoneally, 1 c.c. of the serum and giving the infecting culture by the same route four to six hours later. The following protocol illustrates the plan of the experiment and the results obtained.
Further experiments showed that the serum protects against all serologic types of pneumococci and that there is a particular protective substance for each type. Thus, serum adsorbed with Type I organisms no longer protects against this type but protects against Type I1 cultures as well as before the adsorption and vice versa. This relation exists between all of the types.
A peculiar relationship was found to exist between Type II strains and the subtypes of this group. Thus, serum adsorbed with Type II organisms failed to protect against Type II culture but still protected against the cultures of Types II A and II B. Serum adsorbed with Type II A organisms loses its protective power for II A and II cultures but not for II B cultures. Also, serum adsorbed with II B organisms no longer protects against II B and II cultures but still protects against II A cultures. Hence, in terms of the protective substances in chicken serum, Types II A and II B are main groups with Type II as a subgroup to them both.
Fractionation of the serum by means of ammonium sulphate and dialysis showed that the protective substances adhere quantitatively to the water-insoluble globulin.
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