Characterizing the pregnancy immune phenotype: results of the viral immunity and pregnancy (VIP) study

Abstract

Purpose: The increased risk of morbidity and mortality from certain microbial infections and the demonstrated improvements in the clinical course of some autoimmune diseases support the existence of pregnancy-related alterations in immune status. Elucidating the changes in innate and adaptive immunity during gestation may improve pregnancy outcomes and facilitate the development of targeted therapies for autoimmune diseases.

Method: The Viral Immunity and Pregnancy (VIP) study evaluated over 50 subjects longitudinally at three time points during pregnancy and at two time points post-delivery. Leukocyte enumeration was performed; functional responses of NK cells and CD4 T cells were analyzed, and soluble factors such as cytokines, defensins, and steroid hormones were measured in maternal blood.

Results: In comparison to the post-partum period, the latter part of pregnancy was characterized by significant increases in blood phagocytes and pDCs and decreases in the number and activity of NK and T cells. Alterations were found in antimicrobial proteins and serum cytokines.

Conclusions: These data show that pregnancy is not a period of immunosuppression but an alteration in immune priorities characterized by a strengthening of innate immune barriers and a concomitant reduction in adaptive/inflammatory immunity in the later stages of pregnancy.

Fig. 1

Alpha-defensins 1–3 are increased in peripheral blood during pregnancy. Serum was stored at −80°C until end of study and diluted to 1:100 in PBS before ELISA. All samples from each patient were analyzed on the same plate

Fig. 2

Monocytes and granulocytes increase in peripheral blood during pregnancy. Blood was drawn at each visit and incubated with the appropriate antibodies before being assessed by flow cytometry using Miltenyi cell enumeration beads. Monocytes are defined as CD14+ cells. Granulocytes were calculated based on the subtraction of T, B, NK, monocytes, and DCs from total leukocytes. Data is the mean of all patients and represented as cells per microliter blood. All p values are compared to 6 months post partum. *p < 0.05, **p < 0.005, ***p < 0.001

Fig. 3

Increase in pDCs and mDCs in peripheral blood during pregnancy. Plasmacytoid dendritic cells were defined as CD19−/CD103+ cells, while conventional DCs (mDCs) are defined as CD19−/CD11c+ cells. Data is the mean of all patients and represented as cells per microliter blood. *p < 0.05, ***p < 0.001

Fig. 4

Decrease in CD56 dim cells during pregnancy. a RBC depleaded PBMCs were gated on the CD3⁻ lymphocyte population prior to CD56 analysis. Dot blot shows a representation of analysis of CD56 dim vs. bright staining. b CD56 bright and CD56 dim cells were enumerated using Beckman Coulter Flow-Count fluorospheres. Data is the mean of all patients and represented as cells per microliter blood. ***p < 0.001

Fig. 5

NK cell cytokine secretion during pregnancy is repressed. NK cells were freshly isolated by negative selection and cultured without stimulation (a) or with IL-12/IL-15 stimulation for 20 h (b). Supernatants were assayed by multiplex ELISA. Data is represented as the mean of all patients. All p values are compared to 6 months post partum. *p < 0.05, **p < 0.005, ***p < 0.001

Fig. 6

Decrease in CD3 T cells in blood during pregnancy. Blood was drawn at each visit and incubated with the appropriate antibodies before being assessed by flow cytometry using Miltenyi cell enumeration beads. Data is the mean of all patients and represented as cells per microliter blood (a) or as percentage of CD3 in total blood and percentage of CD4 or CD8 of total CD3+ cells (b). All p values are compared to 6 months post partum. *p < 0.05

Fig. 7

Naïve CD4 T cells have selective cytokine suppression during pregnancy. Naïve CD4 T cells were isolated by negative magnetic bead selection and cultured with TSST for 48 h. Culture supernatants were stored at −80°C until all samples of the patient were taken and assessed by multiplex ELISA. All p values are compared to 6 months post partum. *p < 0.05, **p < 0.005, ***p < 0.001

Fig. 8

B cells are decreased in blood late in pregnancy. Blood was drawn at each visit and incubated with anti-CD19 antibody before being assessed by flow cytometry using Beckman Coulter cell enumeration kit. Data is represented as cells per microliter blood. *p < 0.05