Unusual phenotype of intestinal intraepithelial lymphocytes in the rat: predominance of T cell receptor α/β⁺/CD2⁻ cells and high expression of the RT6 alloantigen

Abstract

The phenotype of intraepithelial lymphocytes (IEL) from the small intestine of adult rats was studied by flow cytometry. Using appropriate monoclonal antibodies the expression patterns of the T cell receptor alpha/beta (TcR2), CD2, the alloantigen RT6 and several other T cell antigens were analyzed. The vast majority of rat IEL expressed TcR2 which is in contrast with data reported for the mouse. The comparison of IEL with lymph node cells revealed major phenotypic differences. Whereas CD2 was present on virtually all lymph node T cells it was found on only less than 5% of IEL. The T cell-specific differentiation antigen RT6 present on only a fraction of lymph node cells was found on about 99% of IEL demonstrating uniform expression with an approximately tenfold higher density. Identity of the detected molecule with RT6 was proven by using congenic controls and by the demonstration of phosphatidylinositol linkage to the IEL membrane. About 86% of IEL expressed CD8 but a substantial proportion of these cells co-expressed the CD4 molecule (34%). Two-color analysis revealed that the CD4+CD8+ double-positive subset completely lacked CD45RB suggesting that they represent memory cells. In the CD4-CD8+TcR2+ subset there was a remarkable heterogeneity of CD5 expression. A substantial number of these cells did not express CD5 despite high density of TcR2. Phenotypic peculiarities found on all or most IEL such as the lack of CD2 and the increased expression of RT6 indicate that the intestinal epithelial environment exerts strong effects on the development and maturation of these cells.

Regional Phenotypic Specialization of Intraepithelial Lymphocytes in the Rat Intestine Does Not Depend on Microbial Colonization

“…IEL comprised both CD3 þ and CD3 ¹ subpopulations, with most of the CD3 þ cells expressing a/b TCR. The CD8aa þ and CD8ab þ subsets were predominant in 2-month-old animals, while CD4 þ IEL (mostly coexpressing CD8a) constituted large numbers by 6 months, corroborating earlier data [6][7][8]22].…”

“…Most information concerning the phenotypes of rat IEL have been obtained by flow cytometric analysis of dispersed cells [6][7][8]22]. The present study was undertaken to determine the distribution of IEL phenotypes in situ.…”

Developmental Changes in Intraepithelial T Lymphocytes and NK Cells in the Small Intestine of Neonatal Rats

“…The phenotypic composition of IEL appears to be influenced by both genetic and environmental factors (8). Most IEL are CD8ϩ, and include cells bearing T cell receptors (TCR) composed of ␥␦ and especially ␣␤ chains (10,11). In addition to the peripheral classic phenotypes [CD8ϩCD4 -and CD8 -CD4ϩ], some IEL exhibit the CD8ϩCD4ϩ (DP) and the CD8 -CD4 -(DN) …”

Cholera Toxin Induces a Transient Depletion of CD8+Intraepithelial Lymphocytes in the Rat Small Intestine as Detected by Microarray and Immunohistochemistry

“…At these ranges, the RT-PCR technique is much more accurate and is more likely to pick up differences in transcript levels. The decrease in RT6 and integrin ␣ E transcripts gives a good indication that IEL are affected, since it has been shown that IEL express RT6 and integrin ␣ E to a much greater extent than lamina propria lymphocytes (6,9,40). The results may also allow a tentative identification of the type of IEL affected.…”

“…Because of their strategic positioning, making up the first line of defense together with the epithelial cells, they are proposed to play an important role in mucosal immunity in relation to both immune defense and intestinal homeostasis (13,44). One problem in studying IEL is the lack of a specific cell marker, although it is known that the cell surface protein RT6, restricted to mature T lymphocytes and a subpopulation of natural killer cells, is expressed at a remarkably high density on IEL (9). In addition, integrin ␣ E seems to be a promising marker for IEL, although expression has also been detected on other T-cell subsets (2,6).…”