Significance of Antibody to Mycoplasma hominis Type 1 as Measured by Indirect Hemagglutination

Abstract

Summary Tanned sheep erythrocytes, sensitized with M. hominis type 1 antigen, were stored in aliquots at — 70°C and used in IHA tests over a period of 3 months. This procedure maintained reproducibility. Fifty-seven per cent of sera from healthy persons of all ages contained antibody when tested by IHA but only 5% contained antibody when tested by CF. indicating the greater sensitivity of the IHA technique. There was an inverse relationship between the presence of IHA antibody in the sera of volunteers before inoculation with the DC63 strain of M. hominis type 1 and the occurrence of illness, indicating the protective effect of this antibody. Most volunteers without antibody prior to inoculation developed an illness and a 4-fold or greater rise in antibody as measured by IHA; no rises were demonstrated by CF. Tests on serial sera obtained from some volunteers indicated that 4-fold or greater antibody rises developed 10 days after inoculation and in some instances the antibody persisted for at least 16 weeks. The greater sensitivity of the IHA technique was not accompanied by a loss of specificity, since only one of 18 volunteers with a 4-fold or greater rise to the DC63 strain developed a 4-fold rise to another mycoplasma species. Only 9 of these volunteers developed a 4-fold rise to the PG21 prototype strain of M. hominis type 1 which was probably due to a minor antigenic difference between the DC63 and PG21 strains. The IHA technique may be valuable in studying, not only experimental infections by other mycoplasma species, but also natural mycoplasma infections.