Phenotypic and functional analysis of human CD3- decidual leucocyte clones

CD3- leucocyte clones were generated from human first-trimester decidualized uterine endometrium in a culture system containing interleukin-2 (IL-2) and phytohaemagglutinin (PHA). All CD3- clones tested by Southern blot analysis had T-cell receptor (TcR) gamma and delta genes in germ-line configuration. Thirty-six CD3- cell clones obtained from eight decidual samples were mostly CD2+CD56+ but, unlike fresh decidual leucocytes, many were also CD16+. Morphological differences were noted between CD16+CD56+ and CD16-CD56+ clones, with the latter cells possessing granules of more variable size. All CD16+ clones expressed strong cytotoxic activity against natural killer (NK) sensitive and NK-resistant cell targets, while CD16- clones had low or negligible activity. Some CD3- clones produced high levels of interferon-gamma, tumour necrosis factor-negligible activity. Some CD3- clones produced high levels of interferon-gamma, tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) upon stimulation, but there was no relationship between specific cytokine production and cell clone phenotype or cytotoxic function. Levels of TGF-beta were generally higher than those produced by decidual CD3+ T-cell clones. Since decidual CD3- CD16- leucocytes have a low proliferative capacity in response to IL-2, and as clones with this phenotype invariably possess low NK cell activity, it is suggested that the NK cell activity of fresh decidual leucocyte populations is mediated largely by the small numbers of CD3- CD16+ cells present.