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It was discovered in the late 1970s and was originally known as leu-3 and T4 (after the OKT4 monoclonal antibody that reacted with it) before being named CD4 in 1984. [5] In humans, the CD4 protein is encoded by the CD4 gene. [6] [7] CD4+ T helper cells are white blood cells that are an essential part of the human immune system. They are often ...
Low CD4 + predicted greater likelihood of intensive care unit admission, and CD4 + cell count was the only parameter that predicted length of time for viral RNA clearance. [42] Despite the reduced levels of CD4 +, COVID-19 patients with severe disease had higher levels of T h 1 CD4 + cells than patients with moderate disease. [43]
Antigen presentation stimulates immature T cells to become either mature "cytotoxic" CD8+ cells or mature "helper" CD4+ cells. An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation.
Type 1 immunity consists of these cells: [5] CD4+ T H 1 cells; CD8 + cytotoxic T cells (T c 1) T-Bet + interferon gamma producing group 1 ILCs(ILC1 and Natural killer cells) CD4 + T H 1 Cells. It has been found in both mice and humans that the signature cytokines for these cells are interferon gamma and lymphotoxin alpha.
CD40 ligand (CD154) is primarily expressed on activated CD4+ T lymphocytes but is also found in a soluble form. While CD40L was originally described on T lymphocytes, its expression has since been found on a wide variety of cells, including platelets, mast cells, macrophages, basophils, NK cells, B lymphocytes, as well as non-haematopoietic cells (smooth muscle cells, endothelial cells, and ...
In humans, CD27 is a good marker for plasma cells; naïve B cells are CD27−, memory B-cells are CD27+ and plasma cells are CD27++. [5] The surface antigen CD138 (syndecan-1) is expressed at high levels. [6] Another important surface antigen is CD319 (SLAMF7). This antigen is expressed at high levels on normal human plasma cells.
The T cell also produces IL-2, which directly influences B cells. As a result of this net stimulation, the B cell can undergo division, antibody isotype switching, and differentiation to plasma cells. The end-result is a B cell that is able to mass-produce specific antibodies against an antigenic target.
With normal aging comes a gradual diminishing of the body's immune system. This phenomenon called immunosenescence is largely due to a decline of T cell function, including the capacity for T FH cells to properly support germinal center responses. [18] This may be in part due to lower CD40L levels on the cell surface of T FH cells in the aged. [19]