T cell deficiency is a deficiency of

T cell A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell r ...

s, caused by decreased function of individual T cells, it causes an immunodeficiency of cell-mediated immunity. 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 B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted o ...

Symptoms and signs

Presentations differ among causes, but T cell insufficiency generally manifests as unusually severe common

viral infection A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells. Structural Characteristics Basic structural characteristics, ...

s (

respiratory syncytial virus Respiratory syncytial virus (RSV), also called human respiratory syncytial virus (hRSV) and human orthopneumovirus, is a common, contagious virus that causes infections of the respiratory tract. It is a negative-sense, single-stranded RNA virus. ...

rotavirus ''Rotavirus'' is a genus of double-stranded RNA viruses in the family ''Reoviridae''. Rotaviruses are the most common cause of diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus ...

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

, and eczematous or

erythroderma Erythroderma is an inflammatory skin disease with redness and scaling that affects nearly the entire cutaneous surface.Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. p. 436. . This term applie ...

tous rashes.

Failure to thrive Failure to thrive (FTT), also known as weight faltering or faltering growth, indicates insufficient weight gain or absence of appropriate physical growth in children. FTT is usually defined in terms of weight, and can be evaluated either by a low ...

and cachexia are later signs of a T-cell deficiency.

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. One sees in the ''partial'' disorder of T cells that happen due to

cell signaling In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself. Cell signaling is a fundamental property of all cellula ...

defects, are usually caused by hypomorphic gene defects. Generally, (micro)deletion of 22Q11.2 is the most often seen.

Pathogens of concern

The main pathogens of concern in T cell deficiencies are

intracellular pathogen Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. Types of parasites There are two main types of intracellular parasites: Facultative and Obligate. Facultative intracellular pa ...

s, including '' Herpes simplex virus'', '' Mycobacterium'' and ''

Listeria ''Listeria'' is a genus of bacteria that acts as an intracellular parasite in mammals. Until 1992, 17 species were known, each containing two subspecies. By 2020, 21 species had been identified. The genus is named in honour of the British pio ...

''.Page 435
in: Also, intracellular fungal infections are also more common and severe in T cell deficiencies. Other intracellular pathogens of major concern in T cell deficiency are:

Diagnosis

The diagnosis of T cell deficiency can be ascertained in those individuals with this condition via the following: * Delayed hypersensitivity

skin test A skin test is a medical test in which a substance is injected into the skin. Examples * Casoni test * Corneometry * Dick test * Fernandez reaction * Frei test * Hair perforation test * Kveim test * Leishmanin skin test * Lepromin * Patch t ...

* T cell count * Detection via culture(infection)

Types

Primary or secondary

* '' Primary (or hereditary) immunodeficiencies'' of T cells include some that cause complete insufficiency of T cells, such as

severe combined immunodeficiency Severe combined immunodeficiency (SCID), also known as Swiss-type agammaglobulinemia, is a rare genetic disorder characterized by the disturbed development of functional T cells and B cells caused by numerous genetic mutations that result in diffe ...

(SCID),

Omenn syndrome Omenn syndrome is an autosomal recessive severe combined immunodeficiency. It is associated with hypomorphic missense mutations in immunologically relevant genes of T-cells (and B-cells) such as recombination activating genes (RAG1 and RAG2), In ...

, and

Cartilage–hair hypoplasia Cartilage–hair hypoplasia (CHH) is a rare genetic disorder. Symptoms may include short-limbed dwarfism due to skeletal dysplasia, variable level of immunodeficiency, and predisposition to cancer. It was first reported by Victor McKusick in 196 ...

. * ''Secondary causes'' are more common than primary ones. Secondary (or acquired) causes are mainly:Page 432
Chapter 22, Table 22.1 in: :* 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

(SCID),

, and

cartilage–hair hypoplasia Cartilage–hair hypoplasia (CHH) is a rare genetic disorder. Symptoms may include short-limbed dwarfism due to skeletal dysplasia, variable level of immunodeficiency, and predisposition to cancer. It was first reported by Victor McKusick in 196 ...

.Medscape > T-cell Disorders
Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD. Updated: May 16, 2011 * ''Partial insufficiencies'' of T cell function include acquired immune deficiency syndrome (AIDS), and hereditary conditions such as

DiGeorge syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent i ...

(DGS), chromosomal breakage syndromes (CBSs), and B-cell and T-cell combined disorders such as ataxia-telangiectasia (AT) and Wiskott–Aldrich syndrome (WAS).

Treatment

In terms of the management of T cell deficiency for those individuals with this condition the following can be applied: * Killed vaccines should be used(not ''live vaccines'' in T cell deficiency) *

Bone marrow transplant Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood in order to replicate inside of a patient and to produce ...

* 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. Furthermore, SCID has an incidence of approximately 1 in 66,000 in California.

References

External links

Pubmed
{{Medicine Immunodeficiency Immune system disorders Infection-related cutaneous conditions Lymphocytes Lymphocytic disorders Hematopathology