T lymphocytes |
Decreased/unaffected from follicular to luteal phase |
Defensive or destructive for the developing embryo depending on
particular subset of cells |
[29, 30, 31, 32] |
T helper cells (Th1, Th2, Th17)
|
Lower levels during mid-luteal and late luteal phase as compared to
early follicular phase.
|
Th1 cells manufacture pro-inflammatory cytokines
Th2 cells cytokines with anti-inflammatory effects
Th17 cells also produce pro-inflammatory type of cytokines
|
[33]
|
B lymphocytes |
Slightly increased toward the end of luteal phase |
Still uncertain, possibly involved in early stage of pregnancy |
[34,
35, 31] |
Uterine dendritic cells (uDCs) |
Controversially immature DCs show an
increasing trend from follicular to luteal phase and reach to peak level
during menstrual phase. However, mature DCs remain unchanged during
reproductive cycle |
Implicated embryo acceptance, remodeling of uterus,
angiogenesis, invasion and differentiation of trophoblasts, decide the
differentiation of progenitors of T cells into Tregs as well as the
activation and proliferation of Tregs |
[30, 36,
37-42] |
Uterine natural killer (uNK) cells |
Show gradual rise from follicular
to luteal phase and reaches maximum level in end of luteal phase and
decidua of pregnancy |
Remodeling of spiral arteries, regulation of
invasion of trophoblasts, angiogenesis enhancement |
[9, 29, 30, 34,
43-46] |
Treg cells |
Proliferate in pre-implantation endometrium, increased at
decidual site for implantation and during early period of pregnancy
until mid-gestation |
Treg cells are crucial for regulating extreme
maternal inflammatory reaction at the site of implantation, participate
in materno-immune tolerance to embryonic allograft mainly during early
stage of pregnancy, blocking maternal effector T cells implicated in
regulating the remodeling of maternal vasculature |
[32, 34, 36,
47-53] |
Lymphocytes |
Significantly declined from follicular to luteal phase |
Potentially toxic for embryo and as a result blocked during successful
gestation |
[31, 32, 35, 54] |
Neutrophil granulocytes |
Show remarkable elevation during late luteal
phase |
Involved in menstruation, breaking down and repairing of tissue.
Exert pro-angiogenic and tolerogenic effects in the decidua of pregnant
women |
[35, 55-57] |
Macrophages |
Increase gradually from follicular phase to luteal phase
and attain peak density prior to menses and during pregnancy |
Participate in the maintenance of corpus luteum, implantation of
blastocyst, spiral artery remodeling, regulation of invasion of
trophoblasts, embryonic protection against intra-uterine infection |
[27, 30, 34, 36, 58-61] |
Mast cells |
Remain unaltered except phenotypical changes during
menstrual cycle and become activated during early and mid-luteal phase |
Involved in the commencement of menses, enhancing the remodeling of
tissue and spiral arteries, supporting the process of implantation as
well as angiogenesis |
[34, 62, 63] |