Veterinary Immunology and Serology

PEYER'S PATCHES

• Some of the Peyer’s patches (PP) present in ruminants intestine function as primary lymphoid organs.
• There are two types of PP in sheep; one in jejunum and the other one is in the ileum and cecum.
• The PP in jejunum persists through out the animal’s life.
• They are pear shaped follicles, separated by extensive inter follicular tissue and contain up to 30% T cells. But ileo-cecal PP reach maximum size before birth, disappears by 15 months of age and cannot be detected in adult sheep.
• The ileo-cecal PPs resembles bursa in birds. B cell differentiation and maturation take place in ileo-cecal PPs but many cells self reactive B-cells die of apoptosis (negative selection) and only very few cells are released into the circulation.