Table 2.

Summary of adaptive immune responses and their proposed role in control of or susceptibility to congenital CMV infection.

Adaptive immunity and susceptibility/protection in congenital CMV infection
Immune effector	Maternal/placental/fetal compartment	Proposed effect on CMV transmission/disease
CD4+ T cells	Maternal compartment Fetal/neonatal compartment	(i) Delayed development of CD4+ T-cell lymphoproliferative response correlates with maternal-fetal transmission (ii) Defective CD4+ immunity; diminished IF-γ and IL-2 production in fetal and early childhood infection (iii) Defective fetal CD4+ response may contribute to congenital CMV infection and disease
T-regs	Maternal compartment	(i) Treg expansion: normal response to pregnancy (ii) ↓ Tregs: correlates with protection against CMV disease in transplant recipients (iii) Relevance to congenital CMV unknown
CD8+ T cells	Maternal compartment Fetal/neonatal compartment	(i) CD8+ response to infection appears unaltered in pregnancy (ii) Fetal CD8+ response to CMV antigens noted as early as week 22 gestation (iii) Exhibit cytolytic properties and elucidate IF-γ   (iv) Some studies raise questions about functionality?
Gammadelta T cells	Neonatal compartment	(i) Fetal gammadelta T cells differentiate and expand in setting of congenital CMV infection (ii) Produce IF-γ and other cytokines (iii) Role in protection of fetus, control of virus not clear
Antibody	Maternal compartment Placental compartment Fetal compartment	(i) Variability in maternal antibody response based on viral strain variation, possibly TLR polymorphisms (ii) Expression of neonatal Fc receptor may paradoxically promote transcytosis of CMV particles across syncytiotrophoblast by low-avidity antibody (iii) High avidity antibody may neutralize CMV at placental interface (iv) Transplacental transfer of therapeutic neutralizing antibody may improve outcome of infected fetus