Mononuclear cells from human neonates are partially resistant to the action of 1,25-dihydroxyvitamin D

Prenatal, perinatal, and heritable influences on cord blood immune responses

BACKGROUND

Maternal and perinatal environmental exposures, as well as inherited factors, may influence neonatal immune responses.

OBJECTIVE

To determine relations of maternal and perinatal exposures to antigen-specific cord blood lymphoproliferative responses.

METHODS

In 427 newborns from a Boston pregnancy/birth cohort, lymphoproliferative responses in cord blood mononuclear cells to stimulation with cockroach (Bla g 2), house dust mite (Der f 1), ovalbumin, and mitogen phytohemagglutinin were measured as stimulation index (SI). We used the Wilcoxon rank sum and chi2 tests to evaluate predictors of ovalbumin SI as a continuous ranked or dichotomous outcome. We used t test and Spearman correlation for univariate testing and linear regression to evaluate predictors of natural log-transformed Bla g 2, Der f 1, and phytohemagglutinin SI. Logistic multivariate regression was applied to evaluate predictors of Bla g 2, Der f 1, and phytohemagglutinin SI dichotomized at 2 or at the median for phytohemagglutinin.

RESULTS

Maternal smoking during pregnancy, inadequate or excessive maternal weight gain during pregnancy, neonate black race/ethnicity (compared with white), and Apgar score less than 8 were each independently associated with increased cord blood mononuclear cell proliferative responses to stimulation with Bla g 2 and/or Der f 1. Maternal history of asthma was associated only with increased lymphoproliferative response to ovalbumin stimulation.

CONCLUSIONS

Distinct fetal and perinatal exposures and black race/ethnicity may be associated with increased cord blood lymphoproliferative responses. The implications of these findings for future development of allergy or asthma are, as yet, unknown.

Responsiveness to 1,25-dihydroxyvitamin D3 is reduced in lymphocytes from osteoporotic women

The purpose of this work was to test the hypothesis that reduced responsiveness of target organs to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] is associated with osteoporosis. Peripheral blood mononuclear (PBM) cells have been previously shown to be a valid model for the action of 1,25(OH)2D3 on its classic target organs in various pathologic and physiologic situations. The responsiveness of lymphocytes to the hormone can be assessed by the extent of inhibition it exerts on the proliferative response to mitogenic lectins. A group of 39 postmenopausal women, at least 10 years after the menopause, participated in the study. Osteoporosis, defined as the presence of at least one nontraumatic vertebral crush fracture, was diagnosed in 19 subjects. Mitogenesis of PBM cells stimulated by phytohemagglutinin and cultured for 72 h in the presence or absence of 1,25-(OH)2D3 (0.03-1 nmol/liter) was assessed by [3H]thymidine incorporation during a 4 h pulse. The maximal inhibitory effect of 1,25-(OH)2D3 at saturating concentration (1 nM/liter) was 74.6 +/- 2.8% (mean +/- SEM) for normal compared to 65.3 +/- 2.9% for osteoporotic women (P = 0.015). The geometric mean of the ED50 values of 1,25-(OH)2D3 was 60% higher in the osteoporotic than in the normal group (P = 0.035). Our data are consistent with the notion that reduced responsiveness of target organs to 1,25-(OH)2D3 is associated with osteoporosis.

1,25-Dihydroxyvitamin D3 acts directly on human lymphocytes and interferes with the cellular response to interleukin-2

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) inhibits mitogen-induced lymphocyte proliferation in peripheral blood mononuclear cell preparations. Receptors for 1,25(OH)2D3 are present in monocytes and are acquired by lymphocytes upon activation. It is not clear whether the hormone inhibits lymphocyte mitogenesis by a direct action on the lymphocyte or only indirectly by affecting the regulatory monocytes. We addressed this question by using highly purified human lymphocyte preparations which contain less than 0.1% monocytes. 1,25(OH)2D3 inhibited the stimulation of purified lymphocytes by phytohemagglutinin and in the presence of fixed accessory cells, which cannot respond to 1,25(OH)2D3. The inhibitory effect attained 35% similar to that obtained in the presence of monocytes. 1,25(OH)2D3 inhibited interleukin 2 (IL-2)-driven stimulation of purified T cells in three different systems: cells treated with a submitogenic concentration of phytohemagglutinin, IL-2-dependent cells which bear receptors for IL-2 and naive cells in the absence of other mitogens. We conclude: (1) the human T lymphocyte is a direct target for 1,25(OH)2D3; (2) 1,25(OH)2D3 inhibits the response of activated, IL-2-receptor-bearing human T cells to interleukin-2.