Passively and actively acquired antibodies forTrichomonas foetusin very young calves

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Abstract
1. The normal agglutinin (n.a.) forTrichomonas foetusfound in all normal adult cattle has a titre of 1:48 to 1:96. N.a. appears to be specific forT. foetusand cannot be absorbed by other flagellates such asT. vaginalisor even completely by the heterologous serological variety ofT. foetusitself. The n.a. appears to be a native constituent of the serum and not to be induced by an exogenous antigen.2. The n.a. passes into the serum of the calf from the maternal colostrum during the first 24 hr. of life. The elimination of the passive n.a. and the development of the autogenous newly formed n.a. in the calf are traced. The passive n.a. disappeared from the 17th to the 55th day and the autogenous n.a. began to appear as a rule from the 35th to the 60th day and was fully established by the 63rd to the 113th day.3. The elimination of the maternal, induced antibody acquired passively from the colostrum took place logarithmically. The rate measured by the half-life ranged from 14 to 20 days, but in one animal which took a very large amount of colostrum it was 57 days.4. The intramuscular injection ofT. foetusantigen into very young calves up to 4 weeks old induced no antibody. When the doses were relatively small the animal produced antibody to antigen given at a later period. When a very large amount was injected in this early period the subsequent capacity to respond to the same antigen but not to other antigens was seriously impaired.The personal encouragement of Prof. H. G. Lamont and the support afforded by the Ministry of Agriculture, Northern Ireland, are gratefully acknowledged.