No abstract

Elevated hemoglobin concentrations have been reported for high-altitude sojourners and Andean high-altitude natives since early in the 20th century. Thus, reports that have appeared since the 1970s describing relatively low hemoglobin concentration among Tibetan high-altitude natives were unexpected. These suggested a hypothesis of population differences in hematological response to high-altitude hypoxia. A case of quantitatively different responses to one environmental stress would offer an opportunity to study the broad evolutionary question of the origin of adaptations. However, many factors may confound population comparisons. The present study was designed to test the null hypothesis of no difference in mean hemoglobin concentration of Tibetan and Aymara native residents at 3,800-4,065 meters by using healthy samples that were screened for iron deficiency, abnormal hemoglobins, and thalassemias, recruited and assessed using the same techniques. The hypothesis was rejected, because Tibetan males had a significantly lower mean hemoglobin concentration of 15.6 gm/dl compared with 19.2 gm/dl for Aymara males, and Tibetan females had a mean hemoglobin concentration of 14.2 gm/dl compared with 17.8 gm/dl for Aymara females. The Tibetan hemoglobin distribution closely resembled that from a comparable, sea-level sample from the United States, whereas the Aymara distribution was shifted toward 3-4 gm/dl higher values. Genetic factors accounted for a very high proportion of the phenotypic variance in hemoglobin concentration in both samples (0.86 in the Tibetan sample and 0.87 in the Aymara sample). The presence of significant genetic variance means that there is the potential for natural selection and genetic adaptation of hemoglobin concentration in Tibetan and Aymara high-altitude populations.

Human cytomegalovirus (HCMV) has been reported to reshape the NK-cell receptor (NKR) distribution, promoting an expansion of CD94/NKG2C + NK and T cells. The role of NK cells in congenital HCMV infection is ill-defined. Here we studied the expression of NKR (i.e., NKG2C, NKG2A, LILRB1, CD161) and the frequency of the NKG2C gene deletion in children with past congenital infection, both symptomatic (n = 15) and asymptomatic (n = 11), including as controls children with postnatal infection (n = 11) and noninfected (n = 20). The expansion of NKG2C + NK cells in HCMV-infected individuals appeared particularly marked and was associated with an increased number of LILRB1 + NK cells in cases with symptomatic congenital infection. Increased numbers of NKG2C + , NKG2A + , and CD161 + T cells were also associated to HCMV infection. The NKG2C deletion frequency was comparable in children with congenital HCMV infection and controls. Remarkably, the homozygous NKG2C +/+ genotype appeared associated with increased absolute numbers of NKG2C + NK cells. Moreover, HCMV-infected NKG2C +/+ children displayed higher absolute numbers of NKG2A + and total NK cells than NKG2C +/− individuals. Our study provides novel insights on the impact of HCMV infection on the homeostasis of the NK-cell compartment in children, revealing a modulatory influence of NKG2C copy number. Eur. J. Immunol. 2012. 42: 3256-3266 Immunity to infection 3257 lifelong latent state, occasionally undergoing reactivation, but may have a pathogenic role in immunodeficient and immunosuppressed patients [1][2][3]. Moreover, HCMV has been associated with atherosclerosis, lymphoproliferative disorders, and glioblastoma, as well as with an accelerated immunosenescence and a shorter lifespan [4][5][6][7]. Vertical transmission of HCMV during pregnancy is considered the most common cause of congenital infection worldwide, affecting ∼0.2-2% of infants and potentially causing fetal lesions [8][9][10]. Though most infected newborns are asymptomatic, ∼10% display a variety of clinical disorders [8,11] potentially leading to important sequelae such as mental retardation and deafness. The type of maternal infection (i.e., primary versus reactivation/reinfection) conditions the risk of congenital infection and the pregnancy stage at which transmission occurs is related to clinical severity [12][13][14][15][16]. Maternal antibodies with neutralizing activity are transferred to the fetus predominantly during the third trimester of gestation and may prevent congenital CMV disease [17]. Among other factors, fetal immune immaturity may determine the outcome of congenital infection [18,19]. An effective defense against HCMV requires the participation of T and NK cells, and the virus has developed different immune evasion strategies [20]. Patients with congenital HCMV infection have been shown to display mature CD8 + T-cell responses [21,22], and an expansion and differentiation of a specific TcR γδ + cell subset has been recently reported [23]. In contrast, information on the role of...

Elevated hemoglobin concentrations have been reported for high-altitude sojourners and Andean high-altitude natives since early in the 20th century. Thus, reports that have appeared since the 1970s describing relatively low hemoglobin concentration among Tibetan high-altitude natives were unexpected. These suggested a hypothesis of population differences in hematological response to high-altitude hypoxia. A case of quantitatively different responses to one environmental stress would offer an opportunity to study the broad evolutionary question of the origin of adaptations. However, many factors may confound population comparisons. The present study was designed to test the null hypothesis of no difference in mean hemoglobin concentration of Tibetan and Aymara native residents at 3,800-4,065 meters by using healthy samples that were screened for iron deficiency, abnormal hemoglobins, and thalassemias, recruited and assessed using the same techniques. The hypothesis was rejected, because Tibetan males had a significantly lower mean hemoglobin concentration of 15.6 gm/dl compared with 19.2 gm/dl for Aymara males, and Tibetan females had a mean hemoglobin concentration of 14.2 gm/dl compared with 17.8 gm/dl for Aymara females. The Tibetan hemoglobin distribution closely resembled that from a comparable, sea-level sample from the United States, whereas the Aymara distribution was shifted toward 3-4 gm/dl higher values. Genetic factors accounted for a very high proportion of the phenotypic variance in hemoglobin concentration in both samples (0.86 in the Tibetan sample and 0.87 in the Aymara sample). The presence of significant genetic variance means that there is the potential for natural selection and genetic adaptation of hemoglobin concentration in Tibetan and Aymara high-altitude populations.