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:'''Systemic disease:''' On T lymphocytes these two co-stimulatory molecules define different functional types; an altered ratio between CD4 and CD8 cells can indicate systemic disease or immune dysfunction :'''Neoplasia:''' Expanded populations of CD4 or CD8 cells (or T cells with unusual expression patterns of these molecules) may represent a malignant clone, and the CD4..."

2023-05-01T13:28:44Z

Created page with " <div style="background-color: #E0EEEE; {{round corners}} padding: 2em 2em; margin-right: 5px;"> :'''Systemic disease:''' On T lymphocytes these two co-stimulatory molecules define different functional types; an altered ratio between CD4 and CD8 cells can indicate systemic disease or immune dysfunction :'''Neoplasia:''' Expanded populations of CD4 or CD8 cells (or T cells with unusual expression patterns of these molecules) may represent a malignant clone, and the CD4..."

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:'''Systemic disease:''' On T lymphocytes these two co-stimulatory molecules define different functional types; an altered ratio between CD4 and CD8 cells can indicate systemic disease or immune dysfunction
:'''Neoplasia:''' Expanded populations of CD4 or CD8 cells (or T cells with unusual expression patterns of these molecules) may represent a malignant clone, and the CD4 or CD8 expression may help identify the disease subtype. However, restricted CD4 or CD8 expression cannot substitute for molecular clonality analysis.

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Function
CD4 and CD8 are transmembrane-glycoproteins that amplify signal generation by the T cell receptor. T cells acquire simultaneous expression of both CD4 and CD8 during their early the thymic stage of development, however when the mature T cells enter the circulation they express either CD4 or CD8 only. CD4 is linked to T-helper cell function, interacting with MHC class II (expressed for example on dendritic cells or B lymphocytes), but is also expressed by immune-presenting cells including monocytes, macrophages, and dendritic cells. CD8 is particularly expressed by cytotoxic cells and interacts with MHC class I (expressed on all nucleated cells) and is also expressed by natural killer cells and dendritic cells.

CD4/CD8 in health
(1) CD4/CD8 ratio: for healthy individuals the ratio in blood lies between 1.5 and 2.5. An inverted ratio is considered an “immune risk” phenotype (occurring in just less than 10% of 20- to 59-year-olds but increasing with age). However, there be quite wide variation depending on a range of factors including infection with the HIV virus.
(2) Absolute counts: These may be more informative than CD4/CD8 ratios: The normal CD4 count should be greater than 400/μL (reference range 500-1,500); CD8 lymphocyte counts should lie in the range to 200-800/μL

CD4/CD8 in mature T cell neoplasia
(1) CD4 proliferations particularly characterise cutaneous lymphomas and T-PLL (although T-PLL may express both CD4 and CD8, or rarely only CD8)
(2) CD8 proliferation typifies ATLL (although simultaneous CD4 expression may occur) and T-LGL

CD4 - Revision history