The accumulation of immunoblasts in extravascular tissues including mammary gland, peritoneal cavity, gut and skin.

The migration of [125I]UdR labelled mesenteric (MLN) and peripheral T immunoblasts (PLN) has been followed in mice with multiple sites attractive to immunoblasts. The sites studied were the inflamed gut (produced by Trichinella spiralis infection), inflamed skin, the peritoneal cavity and the mammary glands of lactating mice. PLN were capable of assembling in all of the four sites and in the presence of both inflamed gut and inflamed skin, PLN accumulated preferentially in the skin. MLN, in contrast migrated only to the gut and mammary glands and not to the skin or peritoneal cavity, and could not be diverted from one site to another. Time course experiments revealed that whereas PLN migrate rapidly through the inflamed gut, they are retained in the skin for at least 3 days.