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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. [ABSTRACT FROM AUTHOR]

It is now accepted that there are present within the peripheral lymphoid tissues of the mammal, lymphocytes which differ in their origin, migratory patterns and lifespan; two major groups have so far been defined, one of thymus-dependent or thymus-derived lymphocytes and another of thymus-independent or bone-marrow derived lymphocytes. These cells which are morphologically indistinguishable when free float lug in the blood or lymph nevertheless segregate from one another into clearly defined compartments whilst resident in or passing through the lymph nodes, spleen or Peyer's patches. The purpose of this article is to summarize some of the experimental evidence for this segregation and to discuss its physiological and immunological implications, it is not intended to be an extensive review of the literature. [ABSTRACT FROM AUTHOR]

Thymus was labelled in vivo by injecting newborn C3H/Bi mice with three or four doses of 2 μc of [3H]thymidine. The labelled thymus was grafted into the kidney capsule of 22-25-day-old intact and thymectomized syngeneic recipients which were killed 18, 41 or 42 days later. The grafts and lymphoid tissue were sectioned and examined by autoradiography after exposure times of up to 26 weeks. Small and medium labelled lymphocytes were seen in the thymus-dependent areas of the lymph nodes and spleen of all recipients provided the sections were exposed for a sufficiently long period. More labelled cells were seen in recipients killed at 18 days than at 41 or 42 days after grafting. It was concluded that these cells were the direct descendants of those cells labelled in the graft. There was no evidence of re-utilization of the isotope label. Most of the cells originally labelled in the graft either lost their label by multiple divisions or were replaced by unlabelled cells; although the epithelial-reticular cells remained heavily labelled. The importance of this last finding is discussed. [ABSTRACT FROM AUTHOR]

A method of orthotopic ovarian grafting in a stock of hooded rats has been described. Intra-strain grafts were established in ten out of eighteen animals and six of these were fertile. Four fertile rats were killed during their first pregnancy but two others kept for 120 and 154 days had several litters of normal size. When ovarian tissue from donors from a stock of albino rats was implanted orthotopically into hooded recipients all the grafts were overwhelmed by homo-graft reaction within 24 days. However, both inter- and intra-strain grafts persisted in the subcutaneous site. Factors affecting the establishment and fertility of the intra-strain orthotopic grafts have been discussed and an explanation for the difference in host response to incompatible grafts according to the site of implantation has been suggested. [ABSTRACT FROM AUTHOR]