1. Why natural killer cells are not enough: a further understanding of killer immunoglobulin- like receptor and human leukocyte antigen 
Diana Alecsandru, M.D., Ph.D., Juan A. García-Velasco, M.D., Ph.D. 
Fertility and Sterility 
Volume 107, Issue 6, Pages (June 2017)
DOI: /j.fertnstert
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2. Figure 1
Placentation is regulated by interactions between maternal killer immunoglobulin-like receptors (KIRs), expressed by uterine natural killer cells (uNKs), and fetal human leukocyte antigen (HLA) C molecules, expressed by extravillous trophoblasts. Maternal and paternal HLA-C (HLA-Cm and HLA-Cp, respectively) are non-self (“foreign”); + = activating KIR; − = inhibitory KIR.
Fertility and Sterility  , DOI: ( /j.fertnstert )
Copyright © 2017 American Society for Reproductive Medicine Terms and Conditions

3. Figure 2 KIR–HLA-C system. Abbreviations as in Figure 1.
Fertility and Sterility  , DOI: ( /j.fertnstert )
Copyright © 2017 American Society for Reproductive Medicine Terms and Conditions