Severe combined immunodeficiency

Introduction to severe combined immunodeficiency Severe combined immunodeficiency disease is a disease in which humoral immunity and cellular immunity are simultaneously severely deficient. Generally, T cell immunodeficiency is more prominent. The number of lymphocytes in the blood circulation of patients is significantly reduced, and mature T cells are absent, and a small number of naive T cells expressing CD2 antigen may appear. Immune functions such as no allogeneic rejection and delayed type hypersensitivity, and no antibody formation. The basic defects of this disease are still unclear, and may be related to the differentiation of stem cells into T and B cell disorders or the developmental abnormalities of the thymus and bursa of the bursa. basic knowledge Sickness ratio: 0.0001% Susceptible people: no specific population Mode of infection: non-infectious Complications: lung abscess pneumonia

Severe combined immunodeficiency etiology

(1) Causes of the disease

The disease is a polygenic genetic disease, patients with significant defects in the T cell and B cell system, inherited by a concomitant or autosomal recessive inheritance (such as Swiss type gamma-globulinemia), most patients (95% ) is a boy, 50% to 60% of sexually inherited recessive inheritance, there are also autosomal recessive inheritance and scattered cases, in some cases may be caused by pluripotent stem cells can not properly develop into B cells and T cells, the whole body Lymphoid tissue is almost completely absent, and it is impossible to synthesize immunoglobulin by itself, and the cellular immune function is almost completely lacking.

(two) pathogenesis

The genetic defect of the hereditary severe combined immunodeficiency disease is the mutation of the chain of the interleukin-2 receptor. Several other interleukin receptors also share this chain with the interleukin-2 receptor, which may explain the serious immunodeficiency of the disease. Sex, early development of T cells requires several interleukin receptors, so if a mutant allele is activated, a female carrier with mutations will "non-randomly inactivate" T cells and cannot survive.

The most common type of autosomal recessive genotype combined with immunodeficiency disease is caused by a mutation in the gene encoded by purine degrading enzyme, adenosine deaminase, purine nucleoside phosphorylase, and the toxicity to lymphocytes comes from sputum metabolism. Accumulation of matter, defects in MHC expression may involve class I or class II MHC molecules, ie HLA-DP, DQ, DR, class I MHC defects due to the encoding of the polypeptide to a similar class I MHC molecule, ie, TAPL or TAP2 Due to gene mutation, the affected children's CD8 cells and natural killer cells are deficient, and the pathogenesis of MHC class II deficiency is complicated, which is related to transactivation factors such as class II transactivation factor on chromosome 15 and defect of RFX5 on chromosome 2. In patients with MHC class II deficiency, CD4 cells are not sufficient for CD8 cells, and their T cells cannot respond to specific antigens. Although the number of B cells is normal, the affected children have hypogammaglobulinemia, and patients with this disease may also have Defects in lymphocyte activation, including CD3 T cell receptors, cytokines such as interleukin-2 production or signaling such as defects in ZAP-70 deficiency.

Severe combined immunodeficiency prevention

1. Strengthen care and nutrition to improve patient resistance and immunity.

2. Prevention of infection should pay attention to isolation and minimize contact with pathogens. For severe combined immunodeficiency disease, the child must be placed in a sterile warehouse for a long time until the immune function is reestablished.

3. Avoid vaccination For newborns with suspected immunodeficiency, vaccination against vaccinia, BCG and other live vaccines should be prohibited to avoid systemic vaccinia caused by vaccination against vaccinia. Infection with BCG causes systemic dissemination and death, and measles should be avoided. Polio vaccine.

Severe combined immunodeficiency complications Complications, lung abscess, pneumonia

There are always sinus and respiratory infections in the course of the disease, Pseudomonas aeruginosa lung abscess, Pneumocystis pneumonia is a common cause of death.

Severe combined immunodeficiency symptoms common symptoms immunodeficiency herpes recurrent infection

The lesions mainly showed lymph nodes, tonsils, and lymph nodes in the appendix. The thymus stayed in the state of the fetus for 6-8 weeks, and there were no lymphocytes or thymus bodies, and the blood vessels were small. Due to the combined defects of humoral and cellular immunity, children are susceptible to various pathogenic organisms. Repeated pulmonary infections, oral candidiasis, chronic diarrhea, and sepsis often occur.

The child develops disease within 1 to 2 months after birth, and is resistant to bacteria, fungi, viruses and protozoal infections. Various infections continue, and skin, lung and gastrointestinal infections often occur in children, almost all children Have diarrhea, stool culture see Salmonella or pathogenic Escherichia coli, persistent skin and mucosal Candida infection, even before the application of broad-spectrum antibiotics, the incidence of sputum increased, can be generalized The child is also not resistant to the virus with weak pathogenicity. Herpes, rubella or varicella virus infection is very serious. The measles course and rash last for a long time. Some patients are vaccinated with vaccinia or BCG, and progressive vaccinia may occur. Or systemic tuberculosis, there are always sinus and respiratory infections in the course of the disease, Pseudomonas aeruginosa lung abscess, Pneumocystis pneumonia is a common cause of death, often accompanied by growth and development disorders.

Severe combined immunodeficiency test

1. Immunological examination B and T cell function were significantly inhibited in vivo and in vitro. Generally, the number of lymphocytes did not change much. In severe cases, lymphocyte decreased significantly. After 6 months of birth, serum immunoglobulin was often lower than O.25g. /L, the number of peripheral blood lymphocytes is often less than 1.5 × 109 / L, and no immune function, no -globulinemia is more common, but in some cases immunoglobulin values can be normal or increased, reactivity to antigen stimulation Very poor, so the inflammatory response seen in infected tissues is very light.

2. Prenatal examination For families born to affected children, prenatal testing of the disease may be performed by classifying fetal blood fluorescence activated cells with monoclonal antibodies or by analyzing enzyme levels in cultured amniotic cells.

3. Carrier detection The mother of a boy with a hereditary genotype can be detected by selective inactivation of an abnormal X chromosome in T cells and B cells.

4. Histopathological examination: the thymus is small, less than 1.0g, composed of dysplastic epithelial cells and interstitial cells, lacking thymus corpuscles and lymphocytes, peripheral lymphoid germinal center and follicular deficiencies, often without pulp cell.

Diagnosis and diagnosis of severe combined immunodeficiency

Detection of ADA activity in patients with red blood cells and fetal cells can confirm the diagnosis and provide a basis for prenatal diagnosis.

Generally not confused with other diseases.

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