Table 1.

Germinal center area size (μm²) in gut-associated lymphoid tissue and in the spleen of laying hens immunized with Escherichia coli F₄ bacterin.

Group	Peyer’s patches	Esophagic tonsils	Pyloric tonsils	Cecal tonsils	Spleen
Control (n = 12)	78,532 ± 890***	9,786 ± 1,389***	47,316 ± 144*	4,731,651 ± 6,789*	499,318.8 ± 26,340***
F4 (n = 18)	354,899 ± 1,245***	18,897 ± 2,567***	51,027 ± 1,877*	5,102,797 ± 8,976*	5,568,072.6 ± 11,380***

The comparison was between groups (F4 and Control) into the same organ; *P < 0.05 and ***P < 0.001.

*Means that the difference between groups was significant. ***Means that the difference between groups was extremely significant.