CCR2 Is Required for the Infiltration of F4/80+ Monocytes Into the Anterior Chamber After the Intracameral Injection of Antigen and the Induction of ACAID

Abstract

Introduction: : Objective: Regulatory T cells induced by the intracameral injection of antigen (ag) are activated by F4/80⁺ peripheral blood mononuclear cells (AC-PBMC).We have shown that after intracameral injection PBMC infiltrate the AC and then recirculate to the thymus and spleen where the AC-PBMC induce regulatory T cells. Here we describe chemokines and chemokine receptors required for the attraction of PBMC to the AC and the induction of AC-PBMC.

Methods: : CFSE-labeled PBMC from WT,CCR2,CCR5 -/- mice were injected iv into naïve WT or CCL2 -/- mice and the mice received an intracameral injection of ag. Six-120 hr later, cell suspensions of irides, spleens and thymi were stained with anti-F4/80 and analyzed by FACS . Irides recovered from mice that received an intracameral injection of ag were compared with naïve mice for the expression of mRNA for chemokine receptors by RT-PCR. PBMC recovered from WT and gene-targeted mice that received an intracameral injection of TNP-BSA or ovalbumin were injected iv into WT mice that were subsequently immunized and a footpad challenged with ag to elicit a DTH response.

Results: : 24 hr after the intracameral injection of ag there was a 2-fold increase in mRNA for the chemokine receptor CCR2 in the irides. An increase in WT and CCR5-/- but not CCR2 -/- CFSE-PBMC was detected in the iris,spleen and thymus after intracameral injection. CFSE-PBMC did not increase in WT mice receiving a subconjuctival injection of ag. Infiltrated PBMC decreased from the iris by 72hr post intracameral injection and increased in the spleen and thymus. WT PBMC infiltrated the irides of CCL2 -/- mice. AC-PBMC from CCR5 -/- but not CCR2 -/- or CCL2 -/- mice transmitted the suppression of DTH.

Conclusions: : The intracameral injection of antigen induces a response to insult to the AC that results in (i) an infiltration of F4/80⁺ PBMC into the AC, (ii) conversion of the infiltrated F4/80⁺ cells to regulatory phenotype and recirculation to the thymus and spleen to activate T cells that regulate cell-mediated immunity.

Keywords: ACAID • immune tolerance/privilege • immunomodulation/immunoregulation