Clonal Expansions of Cd8 ⁺ T Cells Dominate the T Cell Infiltrate in Active Multiple Sclerosis Lesions as Shown by Micromanipulation and Single Cell Polymerase Chain Reaction

Abstract

Clonal composition and T cell receptor (TCR) repertoire of CD4 ⁺ and CD8 ⁺ T cells infiltrating actively demyelinating multiple sclerosis (MS) lesions were determined with unprecedented resolution at the level of single cells. Individual CD4 ⁺ or CD8 ⁺ T cells were isolated from frozen sections of lesional tissue by micromanipulation and subjected to single target amplification of TCR-β gene rearrangements. This strategy allows the assignment of a TCR variable region (V region) sequence to the particular T cell from which it was amplified. Sequence analysis revealed that in both cases investigated, the majority of CD8 ⁺ T cells belonged to few clones. One of these clones accounted for 35% of CD8 ⁺ T cells in case 1. V region sequence comparison revealed signs of selection for common peptide specificities for some of the CD8 ⁺ T cells in case 1. In both cases, the CD4 ⁺ T cell population was more heterogeneous. Most CD4 ⁺ and CD8 ⁺ clones were represented in perivascular infiltrates as well as among parenchymal T cells. In case 2, two of the CD8 ⁺ clones identified in brain tissue were also detected in peripheral blood. Investigation of the antigenic specificities of expanded clones may help to elucidate their functional properties.