Phenotypic Studies of Natural Killer Cell Subsets in Human Transporter Associated with Antigen Processing Deficiency

Jacques Zimmer,Daniel Hanau,Lionel Donato,Huguette Bausinger,François Hentges,Alessandro Moretta,Henri De La Salle,Emmanuel Andrès

doi:10.1371/journal.pone.0001033

Abstract

Peripheral blood natural killer (NK) cells from patients with transporter associated with antigen processing (TAP) deficiency are hyporesponsive. The mechanism of this defect is unknown, but the phenotype of TAP-deficient NK cells is almost normal. However, we noticed a high percentage of CD56bright cells among total NK cells from two patients. We further investigated TAP-deficient NK cells in these patients and compared them to NK cells from two other TAP-deficient patients with no clinical symptoms and to individuals with chronic inflammatory diseases other than TAP deficiency (chronic lung diseases or vasculitis). Peripheral blood mononuclear cells isolated from venous blood were stained with fluorochrome-conjugated antibodies and the phenotype of NK cells was analyzed by flow cytometry. In addition, 51Chromium release assays were performed to assess the cytotoxic activity of NK cells. In the symptomatic patients, CD56bright NK cells represented 28% and 45%, respectively, of all NK cells (higher than in healthy donors). The patients also displayed a higher percentage of CD56dimCD16− NK cells than controls. Interestingly, this unusual NK cell subtype distribution was not found in the two asymptomatic TAP-deficient cases, but was instead present in several of the other patients. Over-expression of the inhibitory receptor CD94/NKG2A by TAP-deficient NK cells was confirmed and extended to the inhibitory receptor ILT2 (CD85j). These inhibitory receptors were not involved in regulating the cytotoxicity of TAP-deficient NK cells. We conclude that expansion of the CD56bright NK cell subtype in peripheral blood is not a hallmark of TAP deficiency, but can be found in other diseases as well. This might reflect a reaction of the immune system to pathologic conditions. It could be interesting to investigate the relative distribution of NK cell subsets in various respiratory and autoimmune diseases.

Highlights

Human natural killer (NK) cells are phenotypically defined as CD32CD56+ lymphocytes
Among the inhibitory receptors (IR), those specific for human leukocyte antigen (HLA) class I molecules recognize either (i) restricted numbers of classical HLA class I alleles in the case of killer immunoglobulin receptors (KIR), (ii) a broad panel of classical HLA class I molecules as well as HLA-G in the case of immunoglobulin-like transcript 2 (ILT2 or CD85j) and (iii) the non classical major histocompatibility complex (MHC) class I molecule HLA-E presenting peptides derived from the signal sequence of classical HLA class I molecules in the case of CD94/NKG2A [4,5]
Deficient patients studied by other groups, so that it is currently unknown if the distribution of CD56bright and CD56dim NK cells is similar or not in these other cases

Summary

Introduction

Human natural killer (NK) cells are phenotypically defined as CD32CD56+ lymphocytes. They constitute a heterogeneous blood cell population and subsets can be defined depending on their level of expression of CD16 and CD56. Among the IR, those specific for human leukocyte antigen (HLA) class I molecules recognize either (i) restricted numbers of classical HLA class I alleles in the case of killer immunoglobulin receptors (KIR), (ii) a broad panel of classical HLA class I molecules as well as HLA-G in the case of immunoglobulin-like transcript 2 (ILT2 or CD85j) and (iii) the non classical major histocompatibility complex (MHC) class I molecule HLA-E presenting peptides derived from the signal sequence of classical HLA class I molecules in the case of CD94/NKG2A [4,5]. NK cells express several IR with ligands different from HLA class I molecules [6]

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