Antigenicity of erythrocytes as analyzed in terms of their cross-reactivity.

The antigenicity of human erythrocytes of four different ABO blood groups and sheep erythrocytes of unknown blood type from different individual sheep were analyzed in terms of their cross-reactivity with antibody-producing cells (plaque-forming cells, PFC) and serum antibody in immunized C57BL/6 and C3H/He mice. The antigenicity of human erythrocytes of different ABO blood groups in the C57BL/6 mice, as determined by the number of specific PFC, was, in decreasing order, AB = A greater than B = O (p less than 0.005). The efficiency of immunogenicity of the human erythrocytes in terms of their cross-reactivity with PFC was, in order, AB = A = B greater than O, and the degree of reactinogenicity was, in order, AB greater than A greater than B greater than O. The order of antigenicity of sheep erythrocytes from different animals, SRBC No. 1 - No. 6, was No. 1 (= No. 2) greater than No. 3 = No. 4 = No. 5 greater than No. 6 in C57BL/6 mice and No. 1 = No. 2 = No. 3 = No. 4 = No. 6 greater than No. 5 in C3H/He mice, determined by the number of specific PFC (p less than 0.01). The cross-reactivity of SRBC No. 1 - No. 6 with PFC demonstrates that the order of immunogenicity of SRBC was No. 1 = No. 2 = No. 3 = No. 4 = No. 5 greater than No. 6 in C57BL/6 mice and No. 1 = No. 2 = No. 3 = No. 4 = No. 6 greater than No. 5 in C3H/He mice, and that of their reactinogenicity was No. 1 greater than No. 2 =No. 3 = No. 4 = No. 5 greater than No. 6 in C57BL/6 mice and No. 1 greater than No. 4 = No. 6 greater than No. 2 = No. 3 greater than No. 5 in C3H/He mice. The cross-reactivity at the antibody level was indicative of the immunologic characteristics of blood cells of low antigenicity (human group O erythrocytes and SRBC No. 5 and No. 6). SRBC No. 5 and No. 6 were somewhat opposed to each other regarding antigenicity in C57BL/6 and C3H/He mice. This signifies the presence of different immunogenic components on SRBC No. 5 and No. 6. The production of anti-SRBC No. 1 antibody reached its peak on the third day after secondary immunization. That of anti- SRBC No. 1, cross-reactive with SRBC No. 6, occurred after a longer latent period, reaching its peak on day 6. This indicates that SRBC No. 1 possesses more than one kind of immunogenic component or immunogenic determinant group on its surface.