Figure 4.

Accumulation of memory B cells, germinal center B cells, and CD4⁺ T follicular helper cells in the adventitia of TA diseased aortas. (A) Accumulation of immune cells (Viability⁻CD45⁺) and B cells (HLA-DR⁺CD19⁺) analyzed by flow cytometry in the adventitial layer of the core of the aortic lesions of a TA patient (P01) as compared to the neck of the same sample. (B) Characterization of B cells in the adventitia of the aortic lesion by flow cytometry shows that most B cells have a memory phenotype (CD27⁺IgD⁻) with some harboring a germinal center phenotype (CD95⁺CD24⁻IgD⁻CD27^high). (C) Flow cytometry analysis of adventitial tissue samples reveals an increase in CD4⁺ T cells in the aortic lesion (top panel), as well as the presence of CD4⁺ T cells harboring a Tfh cell phenotype (PD1⁺CXCR5⁺), as compared to aortic tissues sampled in the aneurysmal neck. (D) CXCR5⁺CD4⁺ T cells from the adventitia of the core aortic lesion are Bcl6^high. (E) CD4⁺ T cells from the adventitia of the neck (gray), non-Tfh cells (CXCR5⁻Bcl6⁻; Red), and Tfh cells (CXCR5⁺Bcl6^high; blue) were analyzed for CD27 and CD45RA expression. As compared to CD4⁺ T cells from the neck, which are a mixture of naive and antigen-experienced (CD27⁻) and memory cells (CD45RA⁻), the adventitia of the core of the aortic lesion contains more antigen-experienced and no naive T cells (CD45RA⁺). Interestingly, Tfh cells in the adventitia are CD45RA^int and display an antigen-experienced phenotype (CD27⁻).