Transcript Reproductive

IMMUNITY & THE DEVELOPING FOETUS
CATEGORY: SYSTEMS & PROCESSES
Reproductive immunology:
immunity and the
developing foetus
Fiona M. Menzies, University of Glasgow, UK
A unique problem
To this day, this question remains relevant and, as yet, incompletely answered and is the
foundation of the field of reproductive immunology.
Immune cells at the maternal-foetal interface
A number of immune cells have been identified within the maternal-foetal interface, including
uterine Natural Killer cells (70%), macrophages (20%), T cells (including CD4+, CD8+, gd T cells,
regulatory T cells) (10%), dendritic cells and B cells (few). The numbers of these cells and roles
that they play differs throughout the various stages of pregnancy.
Protection of the conceptus
Several factors have now been found to be involved in protection of the developing foetus from
attack by the maternal immune system, mainly:
Figure 1.
The Placenta: The
Maternal-Fetal
Interface
1. The anatomical barrier between baby and mother,
through separate circulatory systems within the
placenta (Figure 1).
2. The antigenic immaturity of the fetus. Major
histocompatibility (MHC) antigen expression is
reduced on trophoblast cells on the foetal side of the
placenta.
3. Development of an immunosuppressive
environment within the uterus. Immune cell reactivity
within the uterus is substantially reduced during
pregnancy, thus preventing adverse immunological
responses
against
the
conceptus.
Several
mechanisms are involved including the skewing of
both the local and systemic immune environment
towards a Th2 profile, due to the influence of the
female sex hormones (oestrogen and progesterone).
In addition, the expression of certain molecules (HLA
- G, E, C) on trophoblast cells inhibit the activation
and proliferation of uNK cells and CD8+ T cells.
Umbilical Cord
Intervillous
Space
Spiral artery
Decidua
Maternal
Tissue
Fetal
Tissue
© The copyright for this work resides with the author
Pregnancy presents a complex immunological problem for the mother. Cells and molecules of the
immune system interact in such a way as to prevent the rejection of the semiallogenic foetus (i.e.
sharing only 50% genetic relatedness with the mother, the remainder being with the father) and
support its growth and development. In 1953 Sir Peter Medawar, a pioneer in the field of
transplantation biology, presented a lecture in which he asked the following question:
“The immunological problem of pregnancy may be formulated thus: how does the pregnant mother
contrive to nourish within itself, for many weeks or months, a foetus that is an antigenically foreign
body?”