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Table 3 Fluctuations in immune cells and antibody levels in the female genital tract during the hormonal cycles. Both women and pigs show regional differences in the hormonal regulation of the genital immune system. The antibody fluctuations seem similar in women and pigs but the influx of neutrophils during estrus is specific for pigs. It should be noted that the porcine studies are rather old and only including few animals. LGT – Lower genital tract, UGT – upper genital tract

From: A review of the human vs. porcine female genital tract and associated immune system in the perspective of using minipigs as a model of human genital Chlamydia infection

  Women Pigs
LGT Immune cells Compared to the other regions of the female genital tract (FGT) the vaginal mucosa houses only few lymphocytes and antigen presenting cells (APC) [95]. The cervix, on the other hand, is an immunologic hotspot with the highest concentration of lymphocytes (both T cells and B cells) and APC [55,95]. The number of plasma cells in the vaginal mucosa has been shown to increase during estrous [32,67].
No significant changes, but a slight increase in the number of immune cells in the secretory phase has been shown [57]. No significant changes was seen in the cervical mucosa [35], but a tendency was found, that the number of intraepithelial macrophages increased in estrous and that the number of lymphocytes, plasmacells and macrophages in the subepithelial tissue increased during estrous [32,35].
The activity of cytotoxic CD8 T cell in the lower genital tract (LGT) is persistent during the cycle [96]. The cervix does not show infiltration by neutrophils during estrus [29,67,97].
  Antibody response The total IgG and IgA levels on the mucosa are high after menstruation in the proliferative phase, decrease significantly around ovulation and keeps a medium level in the luteal phase [65,66,98100]. The amount of antibodies on the mucosa has been shown to decrease during estrus/ around ovulation [67].
UGT Immune cells Only few neutrophils are present during the proliferative phase but the number increase towards the menses and are high during the menses [96]. Generally polymorphnuclear leukocytes, macrophages, NK cells and T cells accumulate in the endometrium in the luteal phase during high progesterone level [58,59,96] and the number of macrophages reaches maximum during menses [101]. The uterine mucosa shows an infiltration of neutrophils in proestrous and estrous [29,35,62,97] positively correlated to the estradiol levels [29].
The lymphoid follicles, in the subepithelial tissue develop during the proliferative phase, reach the largest size during midcycle, remain large during the secretory phase and almost disappear at the menses [58,102]. Intraepithelial and subepithelial macrophages and lymphocytes are also more numerous during estrus and early diestrus [29,32] with the peak in number of lymphocytes during early diestrus [104].
Activity of cytotoxic T cells in the mucosa is suppressed in the secretory phase [96]. There were no reportings on difference in size of the lymphoid aggregates during cycle [61].
The number of APC in the fallopian tubes is significantly higher after ovulation in the luteal phase compared to the preovulatory follicular phase [103]. Studies have found either no variation in number of immune cells in the fallopian tube mucosa during the estrous cycle [97] or an increase in number of plasma cells and lymphocytes during estrous [32].
  Antibody response The uterine secretions display the highest levels of IgG around the ovulation/midcycle [57]. Further studies are needed on the fluctuation of antibody levels in the upper porcine FGT.
The Fallopian tubes show a response similar to the lower FGT with a lower level of antibodies around midcycle [57].