Human leukocyte antigen-DQA1*04:01 and rs2040406 variants are associated with elevated risk of childhood Burkitt lymphoma

Burkitt lymphoma (BL) is responsible for many childhood cancers in sub-Saharan Africa, where it is linked to recurrent or chronic infection by Epstein-Barr virus or Plasmodium falciparum. However, whether human leukocyte antigen (HLA) polymorphisms, which regulate immune response, are associated with BL has not been well investigated, which limits our understanding of BL etiology. Here we investigate this association among 4,645 children aged 0-15 years, 800 with BL, enrolled in Uganda, Tanzania, Kenya, and Malawi. HLA alleles are imputed with accuracy >90% for HLA class I and 85-89% for class II alleles. BL risk is elevated with HLA-DQA1*04:01 (adjusted odds ratio [OR] = 1.61, 95% confidence interval [CI] = 1.32-1.97, P = 3.71 × 10-6), with rs2040406(G) in HLA-DQA1 region (OR = 1.43, 95% CI = 1.26-1.63, P = 4.62 × 10-8), and with amino acid Gln at position 53 versus other variants in HLA-DQA1 (OR = 1.36, P = 2.06 × 10-6). The associations with HLA-DQA1*04:01 (OR = 1.29, P = 0.03) and rs2040406(G) (OR = 1.68, P = 0.019) persist in mutually adjusted models. The higher risk rs2040406(G) variant for BL is associated with decreased HLA-DQB1 expression in eQTLs in EBV transformed lymphocytes. Our results support the role of HLA variation in the etiology of BL and suggest that a promising area of research might be understanding the link between HLA variation and EBV control

Rhesus macaque lymph node PD-1(hi)CD4+ T cells express high levels of CXCR5 and IL-21 and display a CCR7(lo)ICOS+Bcl6+ T-follicular helper (Tfh) cell phenotype.

CD4 T follicular helper (Tfh) cells play a unique and essential role in the generation of B cell responses in the lymph node microenvironment. Here we sought to determine if differential expression of PD-1 could be used to delineate Tfh cells in rhesus macaque lymph nodes (LN). CD3(+)CD4(+) T cells were found to harbor a unique subset of cells that expressed the Program death-1 (PD-1) receptor at significantly high levels that were enriched in the LN compartment as compared to peripheral blood. The LN CD4(+)PD1(hi) T cells expressed a predominantly CD28(+)CD95(+) central memory phenotype and were CCR7(lo)ICOS(hi)Bcl6(hi). Additionally, CD4(+)PD1(hi) T cells preferentially expressed high levels of CXCR5 and IL-21 and significantly correlated with Bcl6(+)Ki-67(+) IgG(+) B cells. As Bcl6 is primarily expressed by proliferating B cells within active germinal centers, our results suggest that LN CD4(+)PD1(hi) T cells likely localize to active GC regions, a characteristic that is attributable to Tfh cells. Overall, our findings suggest that high levels of PD-1 expression on CD4(+) T cells in LN of rhesus macaques can serve as a valuable marker to identify Tfh cells and has implications for studying the role of Tfh cells in Human immunodeficiency virus (HIV), Simian immunodeficiency virus (SIV) and other infectious diseases that use the rhesus macaque model

CD4⁺PD-1^hi T cells express significantly high levels of CXCR5 and IL-21 mRNA <i>ex vivo</i>.

<p>(a) Representative dot plots showing the gating strategy and sort purity of CD4⁺PD-1^hi and CD4⁺PD-1^– T cells. b) Fold change in expression of CXCR5 and IL-21 mRNA levels in CD4⁺PD-1^hi T cells relative to CD4⁺PD-1^– T cells. mRNA expression was determined <i>ex vivo</i> in sorted cells by relative qRT-PCR.</p

CD4⁺PD-1^hi T cells significantly correlates with CD20⁺Bcl6⁺Ki-67⁺IgG⁺ B cells in LN.

<p>(a) Representative dot plots showing the gating strategy used for analyzing Bcl6 and Ki-67 expression on IgG⁺ B cells in the lymph node (LN) and b) relative proportions of IgG⁺ B cells in LN expressing Bcl6 and Ki-67. Correlation between LN CD4⁺PD-1^hi T cells and c) CD20⁺Bcl6⁺Ki-67⁺IgG⁺ B cells and d) CD20⁺Bcl6^–Ki-67⁺IgG⁺ B cells in LN.</p

Lymph nodes are enriched for CD4⁺PD-1^hi T cells.

<p>(a) Representative dot plot b) Mean fluorescence intensity (MFI) of PD-1 expression on lymph node CD4⁺ and CD4^– T cells subsets. c) Relative proportions of CD4⁺PD-1^hi T cells and CD4^– PD-1^hi T cells in LN and d) relative proportions of CD3 gated CD4⁺PD-1^hi T cells in LN and peripheral blood mononuclear cells (PBMC).</p

CD4⁺PD-1^hi T cells are predominantly CCR7^lo, Bcl6⁺, IOCS⁺ and express a central memory phenotype.

<p>Representative dot plots showing the expression of a) Bcl6 and ICOS on CD3⁺CD4⁺ T cells and b) CD28 and CD95 expression on lymph node (LN) PD-1^hi and PD-1^–CD4 T cell subsets. c) Relative proportions of Bcl6⁺, ICOS+, CD28⁺CD95⁺ CD4⁺PD-1^hi T cells in LN. d) Representative histograms and e) Mean fluorescence intensity (MFI) of CCR7 expression on LN PD-1^–, PD-1^int and PD-1^hiCD4 T cell subsets.</p