Novel single nucleotide polymorphisms in the human immune inhibitory immunoglobulin-like T cell receptor type 4.

The capacity of antigen presenting cells to induce anergy in T helper cells and elicit the generation of T suppressor cells is regulated by a variety of positive and negative signals. Antigen-specific CD8(+)CD28(-) and CD4(+)CD25(+) T suppressor/regulatory cells induce the upregulation of inhibitory receptors expressed by antigen-presenting cells (APC) belonging to the family of immunoglobulin-like transcripts (ILTs) and downregulation of costimulatory molecules in APC. Immunoglobulin-like immune inhibitory receptor (ILT4), one of the inhibitory receptors expressed by tolerogenic APC, interacts with human leukocyte antigen A, B, and G molecules and transmits negative signals that interfere with the activation of monocytes and dendritic cells. Reported is the identification of two single nucleotide polymorphisms within domain 1 (IgD1) of ILT4 at positions 113 and 144. Domain 1 is part of the distal membrane portion of ILT4, which is engaged in protein-protein interactions between APC and T cells.