Notes on Primary Immunodeficiency

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Primary Immunodeficiency

• These diseases are caused by defects in the body's immune system.

• The most popular PI diseases are: X-linked Agammaglobulinemia (Bruton's Disease), Common Variable Immune deficiency, (Hypogammaglobulinemia), Selective IgA Deficiency Severe Combined Immune Deficiency.

• Many hereditary PI diseases are silent killers if left untreated.

Five main Primary Immunodeficiency Diseases:

• B cell (antibody) deficiencies, combined T cell and B cell (antibody) deficiencies, T cell deficiencies, defective phagocytes, complement deficiencies, deficiencies/cause unknown.

• B-cell malfunction diseases: X-Linked Agammaglobulinemia (XLA), Common Variable Immunodeficiency, Hyper IgM Syndrome, Selective IgA Deficiency, IgG Subclass Deficiency, Severe Combined Immunodeficiency (SCID), Partial Combined Deficiencies, Wiskott-Aldrich Syndrome (WAS), Ataxia-Telangiectasia (AT).

• T-cell malfunction diseases: DiGeorge Anomaly, Cartilage Hair Hypoplasia.

• Phagocyte malfunction diseases: Chronic Granulomatous Disease (CGD), Leukocyte Adhesion Defect (LAD), Chediak-Higashi Syndrome (CHS).

• Diseases of unknown or lesser known origin: Hyper-IgE Syndrome, Chronic Mucocutaneous Candidiasis.

Hyper-IgM (HIM):

• This is a rare disease characterized by overproduction of IgM.

• Individuals are susceptible to bacterial infections, autoimmune disorders, and cancers - targeting tissues and mucosal surfaces.

• The gene TNFSF5 that codes for protein CD154 is mutated.

• The normal immune response: B-cells first produce IgM antibodies that protect tissues and mucosal surfaces.

• With the defective TNFSF5 gene, B-cells cannot communicate with T-cells.

• Treatment: prompt treatment of infections, and IgG therapy through IV.

• Common infections are by Pneumocystis and Cryptosporidium species.

Severe Combined Immunodeficiency:

• Caused by defects in both T and B cell systems.

• Infections occur in infancy.

• Common infections include: pneumonia, meningitis or bloodstream infections.

• Defects in purine salvage pathway, stem cells, cell-surface molecules, IL2.

• Also associated with Letterer-Siwe Syndrome (Omenn Disease).

• These types of infections occur: Fungal (oropharynx, esophagus, skin), Viral (adenovirus, CMV, HSV, measles, rotavirus, varicella), and Bacterial (chronic progressive pneumonitis).

Opportunistic Infections in Immunodeficiency:

• Fungal (chronic mucocutaneous candidiasis, systemic candidiasis).

• Bacterial/Viral Respiratory: pneumonia, pneumonitis, chronic cough.

• Bacterial/Viral Gastrointestinal: esophagitis, gastroenteritis, chronic diarrhea, hepatitis, wasting, distended abdomen.

• Other general diseases include: Graft vs host dieease, leukemia, lymphoma, absence of tonsils, etc.

• Decrease in serum T/B cells.

• Pulmonary infiltrates may be seen in X-rays, absence of thymic shadow.

XLA X Linked Agammaglobulinaemia (Brutons Agammaglobulinaemia):

• Absence of all antibodies.

• There are recurrent bacterial infections involving: encapsulated bacteria such as S. pneumoniae and H. influenzae.

• Diagnosed until age 2-4 years by confirmation of absence of Abs.

• Treatment: antimicrobial therapy with adequate Ig replacement.

• Babies have a chance of developing Pneumocysttis carinii pneumonia.

IgA Deficiency

• Most patients are asymptomatic.

• Anti-IgA antibody reaction occurs in blood transfusions.

Common Variable Immunodeficiency Disease (CVID):

• Deficiency of all, or of some Ig classes, or subclasses.

Defects in Cellular Immunity:

• Defective or no T-cells.

DiGeorge Syndrome:

• Defect in branchial arch embryogenesis.

• No thymus and other organs.

• Defective or no T-cells.

Defective Phagocytes Cause Diseases:

• Chronic Granulomatous Disease.

• Very rare disease with recurrent bacterial infections in children.

• Enlarged lymph nodes with granulomas and scarred skin.

Complementary Deficiency:

• Defective or missing complement system.

• People may have different versions of C4 complement component: C4A and C4B.

• There is increased risk of infections and autoimmune disease.

Additional Readings:

Basic Immunology

1. Introduction to Immunology
2. Cells of Immunology
3. Selection of Lymphocytes
4. Primary Response to Antigen
5. Antigen Processing and Presentation
6. Humoral Effector Mechanism Generator
7. Cell-Mediated Effector Mechanism Generator
8. Vaccination and Immunotherapy
9. Immunodeficiency Diseases
10. Acquired Immunodeficiency Syndrome
11. Hypersensitivities and Autoimmunity Diseases
12. Immunology of Transplantation
13. Immunology of Cancer
14. Immunology Laboratory Technology
15. Acquired Immunity
16. Type II Hypersensitivity Reaction
17. Hypersensitivity Reactions
18. Primary Immunodeficiency
19. Secondary Immunodeficiency
20. Type III Hypersensitivity Reaction
21. Type IV Hypersensitivity Reaction
22. Type V Hypersensitivity Reaction
23. Tumor Immunology
24. Images of Antibodies
25. Th1 vs Th2 cells

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1. Histology of Lymphoid Tissue

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