Physiological Immunosuppression in Pregnancy

Diclaimer: This is not written by blog author but rather taken from:  Lilla Tamasi, Ildiko´ Horvath, Aniko Bohacs et al, " Asthma in pregnancy e Immunological changes and clinical management", Respiratory Medicine (2011) 105, 159-164, Elsevier. This note is not for the commercial use and mainly for educational purposes.

Pregnancy is characterized by a physiological immunosuppression, an immunological tolerance that protects the fetus from maternal immune response against paternal antigens expressed by the fetus.  

Physiological pregnancy has been described as a Th2-dominated state, and current studies show that a trimester dependent, pregnancy-induced increase in regulatory T cell (Tregs) number has a key role in the maintenance of maternal tolerance to paternal antigens during pregnancy, exerting an inhibition on the activation of effector T lymphocytes and NK cells.

Diminished numbers of Tregs in pregnancy were associated with immunological rejection of the fetus as well as preeclampsia and low fetal birth weight.

Of note, Tregs exert inhibitory effects on natural killer lymphocytes responsible for protection against viruses that may contribute to increased susceptibility to viral infections (e.g. influenza) during pregnancy.

Role of ATT in Pregnancy

Question

1) What is ATT?

2) Type of immune response involves

3) Why it is given 2 dose in primid pregnancy

Answer

Tetanus vaccine is an inactivated toxin (toxoid) made by growing the bacteria in a liquid medium and purifying and inactivating the toxin. It involves activation of type II Immune response

It is administer once the quickening felt and can be repeated 2-3 months after first injection in primid women as a booster injection. (Usually 5^th and 7^th months of pregnancy)

For the first time injection, it will stimulate the production of IgM and activation of memory B cell. This IgM could not cross the placenta, hence it action mainly for the protection of the mother.

During the second @ booster dose, it will stimulate the production of IgG. This antibody can cross the placenta and it can give protection for the baby.

Examples of importance of ATT is illustrated in this case.

For woman who undergoes caesarean section, they are always at risk of developing the tetanus from contaminated surgical instrument. ATT are meant to prepare the mother for this event.

As for the baby, the most common source of infection is during the cutting of umbilical cord especially with inadequate sterility of scissors.

Notes: It is different from Anti tetanus human immunoglobulin which are preparation containing IgG immunoglobulin derived from plasma of donors sensitized to tetanus toxoid. It acts by The IgG antibodies acts to neutralize the free circulating exotoxisn of clostridium tetani and prevent its fixation in tissue and its consequences.

Revision on basic immunology- Antigen-APC Interaction