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T cell deficiency is a deficiency of T cells, caused by decreased function of individual T cells, it causes an immunodeficiency of cell-mediated immunity. [1] T cells normal function is to help with the human body's immunity, they are one of the two primary types of lymphocytes (the other being B cells ).
The thymus (pl.: thymuses or thymi) is a specialized primary lymphoid organ of the immune system.Within the thymus, thymus cell lymphocytes or T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders.
The remaining cells exit the thymus as mature naive T cells, also known as recent thymic emigrants. [13] This process is an important component of central tolerance and serves to prevent the formation of self-reactive T cells that are capable of inducing autoimmune diseases in the host.
T cells receptors are generated by randomly shuffled gene segments which results in a highly diverse population of T cells—each with a unique antigen specificity. Subsequently, T cells with receptors that recognize the body's own proteins need to be eliminated while still in the thymus.
Congenital athymia's clinical symptoms are directly related to the thymus's absence and its incapacity to generate T cells with the necessary immune capabilities. An increased vulnerability to bacterial, viral, and fungal infections results from T-cell immunodeficiency. [1] These patients have an especially high incidence of pneumonias.
Regulatory T cells are another type of T cell that mature in the thymus. Selection of T reg cells occurs in the thymic medulla and is accompanied by the transcription of FOXP3. T reg cells are important for regulating autoimmunity by suppressing the immune system when it should not be active. [8]
Nezelof syndrome is an autosomal recessive [6] congenital immunodeficiency condition due to underdevelopment of the thymus.The defect is a type of purine nucleoside phosphorylase deficiency with inactive phosphorylase, this results in an accumulation of deoxy-GTP which inhibits ribonucleotide reductase.
Thymoma with immunodeficiency (also known as "Good syndrome") is a rare disorder that occurs in adults in whom hypogammaglobulinemia, deficient cell-mediated immunity, and thymoma (usually benign) may develop almost simultaneously. [1]: 82 [2] Most reported cases are in Europe, though it occurs globally. [3]