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Updated: Jun 17, 2026

A Plate-based Cytotoxicity Assay for the Assessment of Rat Placental Natural Killer Cell Cytolytic Function
Published on: June 2, 2019
Suppression of natural killer cell cytotoxicity in postpartum women
Maureen Groer1, Nagwa El-Badri, Julie Djeu
1University of South Florida College of Nursing, 12910 Bruce B. Downs Blvd., Tampa, FL 33612, USA. mgroer@health.usf.edu
Problem:
Natural Killer (NK) cell numbers and cytotoxicity are suppressed during pregnancy. Little is known about postpartum NK number and function.
Method Of Study:
Postpartum women (n = 39) were studied at one week and then monthly over the first six postpartum months. The standard natural killer cell cytotoxicity assay (NKCA) was performed. This is a Cr51 release assay from K562 cells cultured with peripheral blood mononuclear cells (PBMCs).
Results:
Data indicate suppression of NK cytotoxicity in postpartum women. Cytotoxicity at each effector:target (E:T) ratio showed a drop from 1 week postpartum, reaching a nadir at around 2 months, and a trend towards recovery of cytotoxicity from 3 to 6 months. Lytic units (LUs) from pre-incubated cells from postpartum women were lower than age-matched, non-pregnant, non-postpartum controls through the fifth postpartum month.
Conclusion:
These data suggest that the postpartum period, like pregnancy, is characterized by decreased NK cytotoxicity activity. This suppressed NK cytotoxic effect may result as a response to interaction with tolerized fetal microchimeric cells accumulated during pregnancy in maternal blood and tissues.
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