CD11a polymorphisms regulate TH2 cell homing and TH2-related disease

Abstract

Background: TH2-dependent diseases vary in severity according to genotype, but relevant gene polymorphisms remain largely unknown. The integrin CD11a is a critical determinant of allergic responses, and allelic variants of this gene might influence allergic phenotypes.

Objective: We sought to determine major CD11a allelic variants in mice and human subjects and their importance to allergic disease expression.

Methods: We sequenced mouse CD11a alleles from C57BL/6 and BALB/c strains to identify major polymorphisms; human CD11a single nucleotide polymorphisms were compared with allergic disease phenotypes as part of the international HapMap project. Mice on a BALB/c or C57BL/6 background and congenic for the other strain's CD11a allele were created to determine the importance of mouse CD11a polymorphisms in vivo and in vitro.

Results: Compared with the C57BL/6 allele, the BALB/c CD11a allele contained a nonsynonymous change from asparagine to aspartic acid within the metal ion binding domain. In general, the BALB/c CD11a allele enhanced and the C57BL/6 CD11a allele suppressed TH2 cell-dependent disease caused by the parasite Leishmania major and allergic lung disease caused by the fungus Aspergillus niger. Relative to the C57BL/6 CD11a allele, the BALB/c CD11a allele conferred both greater T-cell adhesion to CD54 in vitro and enhanced TH2 cell homing to lungs in vivo. We further identified a human CD11a polymorphism that significantly associated with atopic disease and relevant allergic indices.

Conclusions: Polymorphisms in CD11a critically influence TH2 cell homing and diverse TH2-dependent immunopathologic states in mice and potentially influence the expression of human allergic disease.

Keywords: AHR; Airway hyperreactivity; Asthma; CAMP; CD11a; Childhood Asthma Management Program; LD; LFA-1; Leukocyte function–associated antigen 1; Linkage disequilibrium; MIBD; Metal ion binding domain; OVA; Ovalbumin; PE; Phycoerythrin; Rag; Recombination-activating gene; SNP; Single nucleotide polymorphism; T(H)2 cell; WT; Wild-type; allele; allergic disease; biomarker; congenic; homing; polymorphism.

Fig 1

Mouse CD11a exists in distinct allelic forms. The diagram schematically depicts major functional domains of the extracellular domain of CD11a and the amino acid differences between the BALB/c and C57BL/6 mouse strains. TM, Trans-membrane domain.

Fig 2

Effect of CD11a polymorphisms on L major infection. A, Footpad swelling of WT compared with congenic mice infected with L major promastigotes. *P < .001 (n = 5 per group). B-E, Parasite burdens from footpads and spleens at 3 (Fig 2, B and D) and 6 (Fig 2, C and E) weeks. *P < .05. F, Ratio of IL-4– and IFN-γ–producing cells from popliteal lymph nodes at 3 and 6 weeks. *P < .05. G, Ratio of found in inflammatory zone1(Fizz1)/inducible nitric oxide synthase (iNOS), as assessed by using real-time quantitative PCR.*P<.05.

Fig 3

CD11a polymorphisms influence allergic airway disease. A, Respiratory system resistance (R_RS) values comparing BALB/c and BALB/c^C57 congenic mice challenged with PBS or A niger conidia (AN). *P < .001 (n = 3 for BALB/c mice; n = 5 for all other groups). B, Total lung IFN-γ– and IL-4–producing cells. *P < .001. C, Respiratory system resistance values comparing C57BL/6 and C57^Balb congenic mice. *P < .05, (n = 5). D, Total lung IFN-γ– and IL-4–producing cells. *P < .001. E and F, IL-5 and IL-13 levels from lung homogenates. *P < .05 (n = 5). Ach, Acetylcholine; ND, not detectable.

Fig 4

CD11a polymorphisms influence T_H2 cell homing. A, T-cell adhesion to CD54 under dynamic flow. *P < .05 (n = 3). B-E, Rag-deficient mice were reconstituted with labeled T_H2 cells from WT and congenic mice, respectively (Fig 4, B, inset) and intranasally challenged with A niger/OVA to induce T-cell recruitment, after which lung-derived single-cell suspensions were analyzed for donor T_H2 (Fig 4, B [n = 1]; C, and D) and T_H1 (Fig 4, E) cells. *P < .05. Data from one of 3 comparable experiments analyzing 1 × 10⁶ cells per lung.

Fig 5

Association of human CD11a SNPs to allergic disease. A, Location of SNPs within the human CD11a locus; exons are indicated in gray. B, Pairwise r² values for correlations between identified SNPs. Black squares, r² = 1; white squares, r² = 0; gray squares, 0 < r² < 1 with intensity proportional to r². C, Significant correlations between SNPs and the indicated allergy phenotypes. DRSR, Log of dose-response slope to methacholine challenge; ns, not significant; HAYF, hay fever.