Decidual T lymphocyte activation in hydatidiform mole

Aim-To quantify and compare decidual leucocyte subpopulations in complete a nd partial hydatidiform molar pregnancy with those in normal early pregnanc y. Methods-Decidual leucocytes were characterised using an avidin-biotin techn ique and a panel of monoclonal antibodies in formalin fixed, paraffin embed ded decidual tissues from 10 normal first trimester pregnancy terminations and from 13 partial and 13 complete hydatidiform moles. Immunostained cells were fully quantitated and differences between subject groups were analyse d using the Mann-Whitney test. T lymphocyte populations were further charac terised using double immunohistochemical labelling. Results-The numbers and percentages of CD3(+) and CD4(+) T cells were signi ficantly increased in complete hydatidiform moles compared with partial mol es and normal early pregnancy decidua. No differences were found in the num ber or percentage of CD8(+) T cells. The CD8(+) to CD4(+) T cell ratio decr eased significantly in complete mole compared with partial mole and normal decidua. The numbers and percentages of CD45RO(+) cells increased significa ntly in both partial and complete hydatidiform mole compared with normal fi rst trimester decidua. Double labelling confirmed that 50% of CD3(+) T cell s in complete and partial molar pregnancy coexpressed CD45RO, compared with 30% in normal pregnancy. Other leucocyte populations (eGLs, macrophages, B cells, and classical natural killer cells) did not differ between complete and partial mole and normal pregnancy decidua. Conclusions-The presence of an increased population of activated decidual C D45RO(+) T cells in complete and partial molar pregnancy suggests altered m aternal immune responses against molar trophoblast.