Antisera to the mouse milk factor (F), containing up to 0.5 mg. of antibody nitrogen per ml. are readily obtainable in rabbits, especially when adjuvants are added to the antigen.
Quantitative data on the anti-F content of the sera are given, also on the total nitrogen precipitated by the non-casein fraction of C57 mouse milk which does not contain F.
The antisera were also absorbed with casein fractions but the difficulties in the way of quantitative analysis were not overcome.
Antisera to fractions of C57 mouse milk were also obtained and the reactions of F and the C57 proteins with these sera were studied.
The results, as far as they go, are in accord with the earlier belief that the milk factor possesses an immunological specificity not present in normal mouse tissues.