Abstract 46

Background Inuit infants suffer frequent and severe bacterial and viral infections. The immune system in healthy Inuit infants has not been prospectively studied. Objective To compare immune cell phenotypes in healthy Inuit infants and non-Inuit Canadian infants. Methods Healthy Inuit infants from the Canadian Arctic (Iqaluit, Nunavut) and non-Inuit infants from Montreal, Canada. Infants were studied beginning at 1-3 months and blood was drawn on 4 occasions during the 1st year of life. Peripheral blood mononuclear cells (PBMC) were isolated at roughly three month intervals and cryopreserved. Samples were thawed simultaneously for FACS analysis using antibodies for CD4, CD8, B cells (CD19), memory and naive CD4+ T cells (CD45RO and CD45RA), CD69 (early activation marker) on NK cells (CD16) and CD8+ T cells, and CD30 (marker of TH2 phenotype) on CD4+ and CD8+ T cells. Results There were 54 Inuit infants and 109 non-Inuit infants enrolled, and 45 and 99 who completed the study, respectively. Mean PBMC subsets were within the normal ranges for both populations. (Table) Inuit infants had consistently lower % CD4+ T cells and higher % CD8 + T cells than non-Inuit infants, resulting in much lower CD4:CD8 ratios at all time points. For CD4+ T cells, the expression of CD45RO (memory cells) and CD45RA (naive cells) was similar for the two populations for period 1 but significantly different for periods 2, 3, and 4 with the Inuit expressing a larger percentage of memory cells. Expression of CD30 on CD4+ and CD8+ T cells was significantly elevated for the Inuit in periods 2 and 4. Similarly, expression of activation marker (CD69) on CD8+ T cells was much greater in the Inuit for all periods. Activation of NK cells (CD16) occurred much earlier in the Inuit. Conclusion Although all PBMC subsets were within the normal ranges in both populations, the Inuit had consistently lower percent CD4+ T cells and higher percent CD8+ T cells and a lower CD4:CD8 ratio. There is also evidence of early and marked PBMC activation in the Inuit.

Table 1 LYMPHOCYTE SUBSET (% OF TOTAL PBMC)
Full size table