Biomedical subjects
S T Alghali
Publications and source records attributed to S T Alghali.
Hymenolepis citelli and H. diminuta: worm burdens in homologous and heterologous infections in rats.
Primary and secondary infections of Hymenolepis citelli were followed in CFHB rats. In primary infections of 6, 20, and 50 cysticercoids, over 75% of the worms administered became established and grew. Thereafter, survival depended on the intensity of the primary infection. Acquired resistance to homologous challenge infections could be stimulated in rats by prior infection with H. citelli. The growth of secondary worms decreased as the intensity of the sensitizing infection increased. The protective response waned with time in the absence of the primary worms. Cross-protective responses between H. citelli and H. diminuta occur in rats infected previously with either parasite. Retardation in the growth of secondary worms may have an immunological basis.
Immunity to tapeworms: intraspecific cross-protective interactions between Hymenolepis citelli, H. diminuta and H. microstoma in mice.
Interactions between tapeworm species in a single host offer intriguing opportunities for immunological studies that attempt to identify the mechanism(s) underlying protection against cestode infections. Mice that are immunized against Hymenolepis citelli infections were shown to be refractory to subsequent H. diminuta challenge infections. The reciprocity of the response was also demonstrated, although the protection recorded for H. diminuta when mice are sensitized with H. citelli is weaker than that observed when mice are primed with H. diminuta against H. citelli challenge. H. citelli was also shown to be expelled simultaneously during the rejection phase of H. diminuta in concurrent infections, indicating the susceptibility of the former tapeworm to the rejection mechanism initiated by the latter. H. microstoma-immunized mice were shown to be strongly protected against heterologous H. citelli challenge. However, mice primed against H. citelli were not as strongly protected against H. microstoma challenge infections: a statistically significant protection was obtained only after a 12-cysticercoid H. citelli primary infection, although a 6-cyst infection did stunt the growth of H. microstoma challenge worms. It is presently suggested that the cross-protective responses observed in the study between H. citelli, H. diminuta and H. microstoma may have emanated from a specific immunological cross-reactivity due to the sharing of similar immunogens.
Hymenolepis citelli (Cestoda) and Nematospiroides dubius (Nematoda): interspecific interaction in mice.
In mice concurrently infected with Hymenolepis citelli and Nematospiroides dubius, survival of the tapeworm was prolonged, and there was an impairment of the efferent arm of the response to the cestode. The immunological rejection of a six cysticercoid primary H. citelli infection was delayed by the N. dubius infection. The growth of the cestode was poorer in concurrently infected mice, and this effect was rapid, being evident within 4 days of the N. dubius infection. Maximum biomass in the controls was reached on Day 20, whereas in the concurrently infected mice it was reached on Day 25. The induction of acquired immunity to homologous H. citelli infection was suppressed, although the expression of a secondary response against homologous challenge was not abrogated in doubly infected mice. The results are discussed with reference to the immunodepressive effects the nematode is known to have on heterologous antigenic stimulation.