Effects of long-term immunization against the beta-subunit of ovine luteinizing hormone on circulating immune complex formation and on arterial changes in rhesus monkeys
A major safety issue of contraceptive methods based on long-term immunization is the possible effect of circulating immune complexes (CIC) on the arterial wall. We have measured CIC's in 24 monkeys, immunized against the beta-subunit of ovine luteinizing hormone (oLH beta), emulsified with Freund's complete adjuvant, and in 7 nonimmunized controls by Raji assay, Clq assay, and an assay for rheumatoid factor. Eleven of the 24 immunized monkeys had CIC concentrations that were more than two standard deviations above the mean for controls in at least one of the assays. There was no correlation between antibody titer and CIC. Nine immunized and eight control animals on low-fat diets were killed to evaluate the effects of immunization on the artery wall. The cross-sectional intimal area was measured at several sites from projected microscopic images using a sonic digitizer. No statistically significant differences between test and control groups were found. However, when we compared the upper half of the distribution of test and control animals, we found that the mean intimal area of the thoracic aorta of immunized monkeys was twice that of controls and that that of the abdominal aorta was three times as large. These data indicate that long-term immunization against oLH beta induced CIC's in rhesus monkeys. Small increases in the intimal area were found in about half of the immunized animals. The results of this study suggest the need for a larger, more definitive study in which the diet is manipulated so that plasma lipids mimic those of human females in Western society.