RESUMEN
A Mycoplasma-associated immunosuppression of the primary and secondary hemagglutinin response to a common gram-negative antigen of Escherichia coli (014) was demonstrated in the rabbit when preincubated mixtures of common gram-negative antigen and Mycoplasma arthritidis membranes were injected intravenously. A similar immunosuppression was demonstrated only for the secondary hemagglutinin response to a common gram-positive antigen of Staphylococcus aureus when preincubated mixtures of common gram-positive antigen and M. arthritidis membranes were employed as immunizing materials. The immunosuppressive effect occurred with small quantities of M. arthritidis membranes and appeared not to be limited to the host in which arthritogenic properties of the organism were manifested.