Figure 1. The human placenta.

Figure 2. The CBA×DBA/2 murine abortion system: CBA/J (H-2^k) females mated with DBA/2 (H-2^d) females exhibit a high rate of fetal resorptions not seen when mated with BALB/c males (also H-2^d) nor in other matings (such as CBA/J x CBA/J, BALB/c x BALB/C, and C3He x DBA/2 –also H-2^k x H-2^d). Preimmunization of the CBA/J mother with paternal MHC compatible, minor loci disparate BALB/c splenocytes correct resorption rates.

Figure 3. Implantation steps.

Figure 4. Two possible immune defects in implantation. Lack of proper (inflammatory) cytokine production leads to adhesion defects, but conversely late an excess of some of these will activate NK cells towards a cytostatic/Cytotoxic/procoagulant pathway and induce early fetal losses or first trimester abortion.

Figure 5. The T_H1:T_H2 paradigm.

Figure 6. One of the mechanisms of HIV-1 transmission from mother to child: fusion of infected lymphocytes with trophoblasts (here the BeW0 choriocarcinoma cell line).