Animals, Antibodies, Monoclonal, Cell Differentiation, Chick Embryo, Chickens, Fluorescent Antibody Technique, Immunophenotyping, Intestines, Receptors, Antigen, T-Cell, Receptors, Antigen, T-Cell, alpha-beta, Receptors, Antigen, T-Cell, gamma-delta, Spleen, T-Lymphocyte Subsets, Thymus Gland