The occurrence of the feline A blood group antigen on lymphocytes.

Sera from 300 cats were tested for the presence of anti-lymphocytic antibodies. One hundred and nineteen sera showed some activity with the majority (79) reacting only with lymphocytes from blood group A cats. Absorption of two such sera with A, AB and B erythrocytes and absorption of AB system reagents with lymphocytes from A and B blood group cats demonstrated that the A antigen is expressed on both erythrocytes and lymphocytes. Blood group and lymphocyte typing tests of foetuses indicated that the A antigen is present on these tissues as early as 46 days gestation. The erythrocytic B antigen could not be demonstrated on lymphocytes although a single antiserum, which reacted against lymphocytes from group B cats, was found. Several sera containing anti-lymphocytic antibodies which were not related to the AB type were also detected.