Peripheral blood smears of 20 male and 20 female tamarins were examined for the presence of the nuclear drumstick appendage in neutrophils. This chromatin body characteristic of female cells was found in significant numbers of neutrophils from males and in some females was found to be absent or in a lower frequency than expected. The distribution of drumstick-bearing neutrophils among these animals was such that they suggested male-female blood chimerism resulting from prenatal vascular placental anastomoses between fraternal twins of this species. Heterosexual chimerism was confirmed by sex-chromosome analyses of tissues from both male and female animals. The drumstick marker, however, did not provide a reliable quantitative index of chimerism as determined by sex-chromosome analysis. Chimerism was found in blood, bone-marrow, lymph-node, and splenic tissue indicating intermixing of the hematopoietic systems of fraternal twins. A new micromethod utilizing an in vivo diffusion chamber for the procurement of mitotic cells for chromosome spreads was described.
Pregnant mice were exposed to 150 micrograms benzo[a]pyrene (BaP) per gram of body weight during fetogenesis (d 11-17 of gestation) and the progeny were assayed for humoral and cell mediated immune responses at different time intervals after birth. Immature offspring (1-4 wk) were severely suppressed in their ability to produce antibody-(plaque-) forming cells (PFC) against sheep red blood cells (SRBC) and in the ability of their lymphocytes to undergo a mixed lymphocyte response (MLR). Lymphocytes from these progeny showed a moderate to weak capacity to inhabit production of colony-forming units (CFU) in host spleens following transfer with semiallogeneic bone marrow (BM) cells into lethally X-irradiated recipients syngeneic to the BM (in vivo graft-versus-host response, GVHR). A severe and sustained suppression in the MLR and the PFC response occurred from the fifth month up to 18 mo. The in vivo GVHR, also subnormal later in life, was not as severely suppressed as the other two parameters. Tumor incidence in the BP-exposed progeny was 8- to 10-fold higher than in those encountering corn oil alone from 18 to 24 mo of age. These data show that in utero exposure to the chemical carcinogen BaP alters development of components needed for establishing competent humoral and cell-mediated functions of the immune apparatus and leads to severe and sustained postnatal suppression of the defense mechanism. The immunodeficiency exhibited, particularly in the T-cell compartment (MLR, GVHR), before and during the increase in tumor frequency, may provide a favorable environment for the growth of nascent neoplasms induced by BaP.
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