Saad Ah

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.

Testosterone induces lymphopenia in turtles

Owing to the possible role of sex steroids in the immune-neuroendocrine interactions found in lower vertebrates, we attempted to delineate the effect of testosterone propionate on peripheral blood (PB) and the lymphoid organs of the turtle Mauremys caspica. A single intraperitoneal injection of 200 micrograms/g body weight produced thymic involution and intense lymphopenia in the spleen and, less severely, in the PB compartment. It is suggested that lymphocyte redistribution may occur among the various compartments of the body as the main effect of hormone-induced lymphocyte redistribution, although the mechanism in reptiles and mammals is not yet understood.

Ontogeny of con a responsiveness and mixed leucocyte reactivity in the lizard, Chalcidesocellatus

The immune system of phylogenetically key animals will contribute significantly to our understanding of the evolution of immune response in higher vertebrates. Reptiles, being evolutionary precursors of both birds and mammals, represent a pivotal group and thus a study of their immune system is of special significance. Here we described the emergence of T-cell immune capability in the viviparous lizard (Chalcides ocellatus) throughout embryonic development (stages 36-41 of Zada and El Deeb, 1984) and in newborns. The response of embryonic thymocytes (5 X 10(5) cells/ml) to Con A (5 micrograms/ml in culture) was first detected at stages 36-37, increased gradually during successive stages and then declined at birth to yield low responses in newborn lizards. In addition, embryonic thymocytes cultured in two-way MLR, using several combination sets, were significantly responsive at all stages. Our results reveal a degree of immunological T-cell maturation during reptitilian embryonic life which is similar to results in amphibians and mammals, but not clear with respect to fish and birds where comparative information still somewhat limited.

Primary in vitro stimulation of antibody production by lizard splenocytes

Single-cell suspensions of adult lizard (Chalcides ocellatus) spleen have been induced, in vitro, to produce a primary immune response. Using rat red cells (RRBC) as antigen and the culture conditions normally used in most vertebrate species but new for reptilia, it has been found that, in vitro at 37 degrees C, lizard spleen cells produce an antibody-forming response optimal at day 10. The response depends on the number of cultured cells and the dose of antigen, and parallels that obtained in vivo. Leibovitz (L-15) medium supplemented with 10% normal adult lizard serum was a satisfactory culture medium. 2-mercaptoethanol (2-ME), an ingredient used in mammalian cell culture, enhanced antibody production in lizard cells.