Phenotypic analysis of the murine CD4-related glycoprotein, CD223 (LAG-3)

Abstract

CD223 (LAG‐3) is an activation‐induced cell surface molecule, structurally similar to the T cell coreceptor CD4, that binds MHC class II molecules with high affinity. Little is known about theexpression and function of murine CD223. Here, we show that mRNA expression is restricted to the thymic medulla, splenic red pulp and sparse cells in the adult brain cortex. In contrast, surprisingly high expression was seen in defined tracts at the base of the cerebellum and in the choroid plexus of day 7 postnatal brain. mCD223:Ig, but not CD4:Ig, fusion proteins stained cells expressing MHC class II molecules. Analysis of mCD223 cell surface expression was performed with a new monoclonal antibody (mAb) that recognizes an epitope in the D2 domain. Although it blocked mCD223 function in vitro, it did not block binding of mCD223 to MHC class II molecules. While very few TCRα β T cells in the spleen and thymus of naive mice express surface mCD223 (<3 %), ∼ 18 % TCR γ δ T cells and ∼10 % NK cells are positive. This small population of TCRα β T cells are cycling memory T cells (BrdU+, CD44hi, CD62Llo). In contrast, all T cells express mCD223 2–3 days post activation. This study and the anti‐CD223 mAb should greatly assist in the elucidation of CD223 function.

CD4+CD25−LAG3+regulatory T cells controlled by the transcription factor Egr-2

“…In agreement with previous results (26), flow cytometric analysis revealed that Ͼ90% of LAG-3-expressing cells belonged to the CD4 ϩ CD25 Ϫ CD45RB low population (hereafter called CD4 ϩ CD25 Ϫ LAG3 ϩ cells) (Fig. 1A).…”

“…Ectopic expression of LAG-3 conferred regulatory activity to naïve T cells (25). Interestingly, LAG-3 protein was hardly detected on the cell surface of CD4 ϩ CD25 ϩ T cells but was expressed by a sizable population of CD4 ϩ CD25 Ϫ T cells (26). We have found that IL-10-secreting CD4 ϩ CD25 Ϫ LAG3 ϩ T cells show a significant regulatory activ-ity in vivo and characteristically express Egr-2.…”

Expression of lymphocyte activation gene 3 (LAG-3) on B cells is induced by T cells

“…1A, the G15, G37 and G40 Ab, as representatives of a large panel (at least 6 different epitopes are recognized by 12 mAb), stain activated T cells from normal but not from LAG-3 knockout (ko) mice. In activated splenocyte cultures, LAG-3 was upregulated on day 1 and reached plateau on day 3 of activation, consistent with previous observations [8]. In addition, LAG-3 expression was consistently 2.0-2.5-fold higher on CD8 + than CD4 + T cells (Fig.…”

“…Murine LAG-3 transcripts were found in the spleen, thymus and brain. A very small percentage of ab T and NK cells in naive mice express LAG-3, whereas a significant percentage of cd T cells show LAG-3 expression [8].…”

Encounter with antigen-specific primed CD4 T cells promotes MHC class II degradation in dendritic cells

“…Because the TCR on antigen-specific T cells is actually down-regulated after activation (27), it is possible that other MHC-II interacting molecules are involved in the MHC-II cross-linking. Surface expression of the MHC-II binding protein LAG-3 is dramatically enhanced during CD4 T-cell activation (28,29); however, preliminary experiments revealed that LAG-3-deficient OT-II T cells also promoted MHC-II degradation in DCs. The TCR and CD4 are also likely candidates for MHC-II ligands; however, analysis of conjugates between MHC-II antigen-specific T cells lacking CD4 and antigen-loaded DCs is not technically possible.…”