Horse anti-type XIV Pneumococcus sera behave as cold agglutinins recognizing developmentally regulated antigens apart from the Ii antigens on human erythrocytes.

Haemagglutination studies with horse anti-type XIV pneumococcus sera have shown that they resemble cold agglutinin sera with anti-I specificity reacting more strongly with adult human erythrocytes than cord erythrocytes. However, their substantial reaction with iadult erythrocytes suggests that they react with other developmentally regulated antigens in addition to the I and i antigens.