Effect of selection for high and low antibody response against sheep red blood cells on hormonal profile during immune response in chickens

Abstract EN

Two experiments were conducted in this study using two lines of Fayoumi chickens divergently selected for high (H) and low (L) antibody response against sheep red blood cells (SRBC) for four generations.

The objectives of this study are to compare humoral and cell mediated immune responses between the lines, as well as to monitor the T3 and corticosterone hormone profile during the initiation of the immune responses.

In the first experiment one hundred male chicks of each line were primary injected intramuscular with either 1 ml 25% SRBC suspension or saline at 50 and secondary reinjected at 80 days of age.

Blood samples were collected at 0, 1, 3, 6, 9, 12 and 24 h and at 3, 7 and 10 days following primary and secondary injection.

The results showed that H line produced significantly higher primary and secondary antibody titer than L line at 7 and 10 days post injection.

The results showed that T3 levels decreased significantly at 3 h in H line and at 3, 6 and 9h in L line, then remained at low levels till 10 days post primary SRBC injection as compared to 0 h.

Within both H and L lines, the T3 level showed insignificant differences between 0 hr and at any time post secondary SRBC or saline injection ( except that in H line at 3h post SRBC injection).

In both line there was a significant increase in corticosterone levels at 24h as well as at 3, 7 and 10 days post primary, and at 3,7 and 10 days post secondary SRBC injection as compared to 0 h.

In the second experiment, one-hundred and twenty male chicks of each line were injected intradermally into wattle with either 100 µg PHA-P or saline at 56 days of age to monitor the delayed type hypersensitivity (DTH) reaction.

Blood samples were collected at 0, 3, 6, 9, 12 and, 24 hs post injection.

The results indicate that H line had higher DTH value at 12 and 24 h than that in L line at the same time point.

There was no remarked change in the level of T3 or corticosterone between PHA-P and saline injected birds at any time point following injection within both lines.

In conclusion, the results of T3 or corticosterone levels in the current study may explain that the initiation of humoral immune response involves the activation of HPT- and HPA-axis.

While this axis is not involved in delayed type hypersensitivity reaction.