Quantitative bone histomorphometry and circulating T lymphocyte subsets in postmenopausal osteoporosis.

To explore the influence of the immune system on the development of osteoporosis, 19 untreated postmenopausal women with osteoporosis were studied by means of quantitative histomorphometry of the ilium and an analysis of T lymphocyte subsets in the peripheral blood. Osteoporotic women had lower OKT3+ and OKT8+ counts and a higher OKT4+/OKT8+ ratio than nonosteoporotic control subjects. Linear regression analyses disclosed that the age of subjects correlated with bone mineral density (BMD; r = -0.634, p less than 0.01) and some of the histomorphometric parameters for bone formation (r = -0.694 to -0.467, p less than 0.01-0.05). The number of OKT4+ cells showed weak but significant negative correlation with the parameters for bone resorption (r = -0.549 to -0.462, p less than 0.05). In a multiple regression analysis, the advanced age, the increase in OKT3+, and the decrease in OKT4+ and OKT8+ counts were shown to be significant predictors for the decrease in BMD (R = 0.882, p less than 0.01). According to the regression formula obtained from the analysis, the parameters for bone formation were related only to the age of subjects whereas those for bone resorption were tightly associated with the number of OKT4+ and OKT8+ cells but not with the age of subjects. These results indicated that, in addition to the age factor, abnormalities of the peripheral T lymphocyte subsets, especially those of OKT4+ and OKT8+ cells, are closely associated with the decrease in bone mass in postmenopausal osteoporosis, supporting the causal relationship between T lymphocyte functions and the development of postmenopausal osteoporosis.