Biased accumulation of T lymphocytes with "memory"-type CD45 leukocyte common antigen gene expression on the epithelial surface of the human lung.

Abstract

Although all T lymphocytes express antigen-specific receptors, there is increasing evidence that a population of blood T cells are "naive" in that they respond poorly to recall antigens, while other blood T lymphocytes are "memory" cells in that they proliferate readily in response to recall antigens, function efficiently as immune effector cells, and express surface molecules involved in antigen presentation and adhesion to endothelial cells and extracellular matrix components (1-5). The populations of "naive" and "memory" T cells are defined by the expression of the family of CD45 leukocyte common antigens coded by a single 130 kb, 33 exon gene (6) . The CD45 gene uses differential splicing to generate multiple mRNA transcripts that direct the synthesis of 220, 205, 200, 190, and 180 kD glycoproteins (7-12) . While the 220 and 205 kD glycoproteins are expressed on the surface of "naive" T cells and are detected by the 2144 mAb, the 180 kD glycoprotein is expressed only on "memory" T cells and is detected by the UCHL1 antibody (11-14) . Relative to the 33 exon CD45 gene, the mRNA transcript coding for the 220 kD 2144 + protein contains the sequence information of all 33 exons, while the transcript coding for the 205 kD 2144 + protein is missing residues coded by exon VI (12, 13) . In contrast, the CD45 mRNA transcript coding for the 180 kD UCHL1 + protein is missing exons IV, V,.A number of observations about T cells at sites of chronic inflammation suggest that the relative proportions of "naive" and "memory" T cell populations can vary within the body . In this regard, while blood T cells include both "naive" and "memory" T cells in approximately equal proportions, T cells participating in chronic inflammatory diseases in tissues are mostly comprised of"memory" T cells (15)(16)(17)(18) .

HIV-related lung disorders

“…Less cellular activation is seen and nonspecific cytokine secretion resolves. What remains is persistent low level IFN-γ production from resident memory cells that inhabit the lung [7], which in turn maintains the BAL concentration of IFN-γ inducible chemokines leading to the normal trafficking of these cells into the alveolar space rather than a massive influx of non-specific inflammatory cells. This results in a much tighter relationship between chemokine concentrations in the lung and lung lymphocyte numbers.…”

“…During the initial antigenic response, memory B and T cells are also created which allow the host to respond more rapidly upon re-exposure to the same antigen. Importantly, memory cells make up the predominant resident lymphocyte population in the normal lung [7].…”

The repertoire of T-lymphocytes recovered by bronchoalveolar lavage from healthy nonsmokers

“…In fact, lung lymphocytes display the very late activation-1 (VLA-1) surface antigens [1] at a much higher rate than early activation markers, such as the interleukin-2 (IL-2) receptor [2]. They also have low IL-2 messenger ribonucleic acid (mRNA) expression and a "memory" T-cell phenotype, as defined by the CD45 RO membrane molecule [3]. Therefore, it is likely that BAL T-cells represent a compartmentalized lymphoid population with a low capability of proliferation, that is thought to be less efficacious than other more organized structures in driving an optimal immunization against new antigens [4].…”

An industrial risk: Beryllium

“…37 KBH'da ise BAL'daki mevcut makrofaj ve lenfositlerin sayı ve oranında belirgin bir yükseliş görülür. 9,38 Bu lenfositlerin çoğu CD4+ T hücreleri-dir 38-40 ve KBH'nın patogenezinde önemli rol oynarlar. 24,37,41,42 KBH'lı bireylerin akciğerlerinde CD4+ T hücreleri aktive olduğunda, bu hücreler klonal olarak proliferasyon göstermekte ve IL-2, IFN-γ ve tü-mör nekroz faktörü (TNF-α) gibi Th-1 tipi sitokinleri salgılamaktadır.…”