γδT cells of human early pregnancy decidua: evidence for local proliferation, phenotypic heterogeneity, and extrathymic differentiation pathway

52

Abstracts

medium. Hence, GM-CSF produced by the endometrium is likely to exert influence on events within the uterine cavity, particularly prior to fertilization and during the peri-implantation period when the endometrium may be the major source of this cytokine. Keywords:

Endometrium;

Epithelium;

GM-CSF;

Vectorial

secretion

1361

y~3T cells of human early pregnancy decidua: evidence for local proliferation, phenotypic heterogeneity, and extrathymic differentiation pathway Lucia Mincheva-Nilsson”, Maria Kling”, Sten Hammarstriimb, Olga Nagaeva”, Karl-G&a Sundqvist”, Marie-Louise Hammarstriimb, Vladimir Baranovb. “Department of Clinical Immunology, UmeB University, 90185 Umed, Sweden; bDepartment of Immunology, Urned University, 90185 Umed, Sweden The uterine mucosa in pregnancy, the decidua, allows placenta formation and survival of the fetus in spite of the fact that it is semiallogeneic. Decidua contains large numbers of lymphocytes of which CD56+ cells dominate, followed by T cells expressing either a/3- or y6-TCR. We have investigated the developmental relationship between the CD56- and TCRyS expressing cells in early pregnancy decidua using dual labelling immunoelectron microscopy, immunoflow cytometry and cell fractionation. Lymphocyte subpopulations were, in addition, analysed for expression of the cytokine receptor for IL-7 and c-kit, and for mRNA expression of recombinase activating genes (RAG) 1 and 2. Four different cell populations could be distinguished: CD56 + brigh’, CD56 + di”/TCR$ + low, CD56fdi”/TCR$ + high, TCR$ + low. RAG1 and 2 were expressed in the CD56 + bright cells and to a limited degree in CD56 + d’“/TCRyG +row cells. C-kit was preferentially expressed on the CD56 + brightcells while IL-7R was preferentially expressed on CD56 + di”/TCRyG + low and CD56 + di”/TCRyG + high cells. The CD56 + dim/ TCR y8 + lowand the CD56 + dim/TCRyG + highcells displayed the characteristic morphology of large granular lymphocytes while single positive TCRyG + low cells were usually smaller and did not contain cytoplasmic granules. The V6 1 gene segment was almost exclusively utilized in the TCR. $T cells in mitosis were seen. We suggest that human early pregnancy decidua is a transient site for extrathymic maturation and that the progenitors of TCR$ + cells are bone marrow derived immature cells expressing the CD56 (N-CAM) homing receptor. Keywords: maturation

Decidual

y6T-cell

differentiation;

RAG;

IL-7R;

Extrathymic