Immunological changes during pregnancy in the viviparous lizard, Chalcides ocellatus

Splenic cells from pregnant and non-pregnant viviparous lizards (Chalcides ocellatus) were stimulated in vitro with the mitogens, concanavalin A (Con A), phytohemagglutinin (PHA) and Escherichia coli lipopolysaccharide (LPS). Cell cultures from pregnant animals were significantly less responsive to Con A and PHA than comparable cultures from non-pregnant animals. The response was depressed during the first period of pregnancy and remained low in magnitude until parturition. By contrast, the response of maternal splenic cells to LPS was reduced in pregnant lizards only during advanced pregnancy. The drastic decrease in mitogenic responsiveness was associated with marked involution of the maternal spleen. These findings strongly suggest that pregnancy impairs the immunoreactivity of viviparous lizards. Possible mechanisms for this impairment and the relationship to circulating levels of sex hormones are discussed.