T cell deficiency

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).^{[medical citation needed]}

T cell deficiency
Human T Cell
Specialty	Immunology
Symptoms	Eczematous[1]
Types	Primary or Secondary[2]
Diagnostic method	Delayed hypersensitivity skin test, T cell count[1][3][4]
Treatment	Bone marrow transplant, Immunoglobulin replacement[1][2]

Symptoms and signs

Presentations differ among causes, but T cell insufficiency generally manifests as unusually severe common viral infections (respiratory syncytial virus, rotavirus), diarrhea, and eczematous or erythrodermatous rashes.^[1] Failure to thrive and cachexia are later signs of a T-cell deficiency.^[1]

Mechanism

In terms of the normal mechanism of T cell we find that it is a type of white blood cell that has an important role in immunity, and is made from thymocytes.^[5] One sees in the partial disorder of T cells that happen due to cell signaling defects, are usually caused by hypomorphic gene defects.^[6] Generally, (micro)deletion of 22Q11.2 is the most often seen.^[7]

Pathogens of concern

Further information: Intracellular pathogen

The main pathogens of concern in T cell deficiencies are intracellular pathogens, including Herpes simplex virus, Mycobacterium and Listeria.^[8] Also, intracellular fungal infections are also more common and severe in T cell deficiencies.^[8] Other intracellular pathogens of major concern in T cell deficiency are:

• Mycobacterium avium intracellulare^[9]
• Salmonella species^[9]
• Rhodococcus equi^[9]
• Pneumocystis jirovecii^[9]
• Toxoplasma gondii^[9]
• Cryptosporidium parvum^[9]
• Leishmania species^[9]
• Herpesviridae (herpes simplex, cytomegalovirus and varicella zoster)^[9]
• Cryptococcus neoformans^[9]
• Histoplasma capsulatum^[9]

Diagnosis

The diagnosis of T cell deficiency can be ascertained in those individuals with this condition via the following:^[1][4][3]

• Delayed hypersensitivity skin test
• T cell count
• Detection via culture(infection)

Types

Primary or secondary

Lymphoma

• Primary (or hereditary) immunodeficiencies of T cells include some that cause complete insufficiency of T cells, such as severe combined immunodeficiency (SCID), Omenn syndrome, and Cartilage–hair hypoplasia.^[1]
• Secondary causes are more common than primary ones.^[9] Secondary (or acquired) causes are mainly:^[9]

• AIDS
• Cancer chemotherapy
• Lymphoma
• Glucocorticoid therapy

Complete or partial deficiency

• Complete insufficiency of T cell function can result from hereditary conditions (also called primary conditions) such as severe combined immunodeficiency (SCID), Omenn syndrome, and cartilage–hair hypoplasia.^[1]
• Partial insufficiencies of T cell function include acquired immune deficiency syndrome (AIDS), and hereditary conditions such as DiGeorge syndrome (DGS), chromosomal breakage syndromes (CBSs), and B-cell and T-cell combined disorders such as ataxia-telangiectasia (AT) and Wiskott–Aldrich syndrome (WAS).^[1]

Treatment

Harvested bone marrow in preparation for transplant

In terms of the management of T cell deficiency for those individuals with this condition the following can be applied:^[2][1]

• Killed vaccines should be used(not live vaccines in T cell deficiency)
• Bone marrow transplant
• Immunoglobulin replacement
• Antiviral therapy
• Supplemental nutrition

Epidemiology

In the U.S. this defect occurs in about 1 in 70,000, with the majority of cases presenting in early life.^[1] Furthermore, SCID has an incidence of approximately 1 in 66,000 in California.^[10]

See also

• B cell deficiency