Images of CD4
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Generation and Immune Regulation of CD4+CD25−Foxp3+ T Cells in Chronic Obstructive Pulmonary Disease

Without CD4+ T cell help, cytotoxic effectors would not existSmall change for you. Big change for us!

Illustration shows activation of a CD4-plus helper T cell. An antigen-presenting cell digests a pathogen. Epitopes from this pathogen are presented in conjunction with MHC II molecules on the cell surface. A T cell receptor and a CD8 receptor, both on the surface of the T cell, bind the MHC II-epitope complex. As a result, the helper T cell becomes activated and both the helper T cell and antigen-presenting cell release cytokines. The cytokines induce the helper T cell to clone itself. The cloned helper T cells release different cytokines that activate B cells and CD8+ T cells, turning them into cytotoxic T cells. The cytotoxic and binds the MHC I-epitope complex on an infected cell. The cytotoxic T cell then releases perforin molecules, which form a pore in the plasma membrane, and granzymes, which break down proteins, killing the cell.