We examined the appearance of intestinal intraepithelial lymphocytes (IEL) during the first 12 wk of life to gain insight into postnatal factors that contribute to the differences found between IEL in the large and small intestines of adult mice. Intestinal T cells were very infrequent at birth, but increased in number in the large and small intestine during the first 4 wk of life and then stabilized. The small intestinal epithelium at 2 wk of age contained mostly T cell receptor (TCR) ␣␤ϩ, CD2ϩ T cells, unlike IEL in adult mice, which were composed of nearly equal proportions of CD2Ϫ, TCR ␣␤ϩ and TCR ␥␦ϩ cells. Between 2 and 3 wk of age, TCR ␥␦ϩ, CD2Ϫ IEL increased greatly in the small intestine, whereas TCR ␣␤ϩ cells expressing CD2 decreased. By contrast, IEL in the large intestine at 2 and 3 wk of age were mostly TCR ␣␤ϩ, CD2ϩ T cells similar to large intestinal IEL in adult mice. And finally, the expression of CD69 increased earlier and to higher levels on TCR ␣␤ϩ and TCR ␥␦ϩ IEL in the small intestine than in the large intestine. Our results demonstrate that IEL in the large and small intestine are phenotypically similar during suckling and that differences between these populations are established after weaning. Furthermore, the earlier accumulation of IEL with an activated adult IEL phenotype in the small intestine suggests that these T cells mature or expand in the gut and contribute to the maturation of immune function during postnatal life in mice. The mucosal immune system of the intestine consists of lymphocytes located in anatomically distinct, but functionally related regions comprising the largest immune effector site in the body. Lymphocytes located within the intestinal epithelium are almost exclusively T cells, called IEL (1). SI-IEL are mostly CD8ϩ, CD4Ϫ T cells (60 -70%), which express a TCR composed of ␥ and ␦ chains (TCR ␥␦; 40 -50%) or ␣ and ␤ chains (TCR ␣␤; 50 -60%) (1-3). This is unlike T cells found in peripheral blood and nonmucosal lymphoid organs, which are mostly TCR ␣␤ϩ cells that express either CD4 or CD8 in nearly equal proportions. Furthermore, most SI-IEL in mice express a unique form of CD8, the CD8␣␣ homodimer, whereas the majority of CD8ϩ T cells in the lymph node and spleen express the CD8␣␤ heterodimer (1, 4, 5). Other T cell surface proteins distinguish IEL from peripheral T cells. The majority of IEL isolated de novo express the activation antigen, CD69, and a unique mucosal integrin, ␣ E␤7 , whereas the majority of resting T cells in the periphery lack these proteins (6 -8). Furthermore, most SI-IEL do not express the lymph node homing receptor, CD62L, or the costimulatory ligand, CD2, proteins that are expressed by a majority of T cells found in lymph node and spleen (6,7,9). Taken together, these data demonstrate that IEL are distinct from T cells found in nonmucosal sites.Intestinal mucosal T cells share some common features, although there are important regional differences between IEL in the small and large intestine and between IEL and T cells found in the lamina...

The nature and extent of the reactions involved in the two-step, wet-fixation durablepress process of Getchell and other processes have been determined by means of a periodate oxidation method. The wet-fixation, durable-press process is shown to differ from the acid colloid process and other wet-fixation procedures. The variations show up in terms of the concentration of the methoxymethylol compound and reactant fixed on the fiber and the extent to which covalent crosslinking of cellulose occurs.The results indicate that in the wet-fixation, durable-press process the methoxymethylmelamine results in only a relatively low degree of cross-linking, but it is, nevertheless, durably fixed to the fabric, probably as a low molecular-weight polymer. It also appears to interact with and moderate the strong cross-linking tendency of the reactant. Predrying the fabric before wet-fixation leads to a greater degree of crosslinking. The nature of the reactant influences the results obtained. The degree of methoxymethylation of the melamine compound also has an effect on the final result which appears to be related to the ability of the methoxymethylmelamine to resist the rinsing (neutralization) step after wet fixation which, in turn, appears to be related to the tendency of the various methoxymethylmelamines to form low polymers.

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