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Karan - MBBS Year 1: Respiratory Week 4 > Immune Deficiencies and Autoimmunity > Flashcards

Immune Deficiencies and Autoimmunity Flashcards

1
Q

What is immunodeficiency?

A
  • Partial/full impairment of immune system function/development
  • Body unable to effectively resolve infections - high risk of recurrence
  • Associated with autoimmunity, lymphomas, other cancers
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2
Q

What is the difference between primary and secondary immunodeficiencies?

A
  • PRIMARY - congenital
  • SECONDARY - acquired from disease/environmental factors
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3
Q

What are the categories of primary immunodeficiencies?

A
  • Antibody deficiencies
  • Combined immunodeficiencies
  • Phagocytic cell disorders
  • Complement deficiencies
  • Disorders of immune regulation
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4
Q

What are the features of the following immunodeficiencies:
- B cell deficiencies
- T cell deficiencies
- Innate immune deficiencies

A
  • B cell - reduced serum Ig levels and absent/reduced follicles in lymphoids. Involved in pyogenic bacterial infections
  • T cell - reduced in lymphoids - reduced reactions to antigens. Involved in viral infections
  • Innate immune deficiencies - dependent on which component of innate immunity defective
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4
Q

What are the clinical mainfestations of immune deficiencies?

A
  • GI, haematologic and infectious diseases
  • Autoimmune/rheumatic diseases - arthritis and SLE
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5
Q

Give examples of infectious diseases someone with immune deficiencies may suffer from.

A
  • Recurrent sinopulmonary infections e.g sinusitis, bronchitis and pneumonia most common presenting manifestations
  • Recurrent sysetmic infections e.g bacteremia and meningitis
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6
Q

What is the most common type of presenting infections in patients with primary antibody deficiencies?

A

RESPIRATORY

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7
Q

When are autoimmune/rheumatic diseases most common?

A
  • Selective IgA deficiency
  • CVIDs
  • Deficiencies of complement system
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8
Q

What are some types of primary antibody deficiencies (humoral immunity deficiencies)?

A
  • X-linked agammaglobulinema (XLA), Bruton’s
  • CVIDs
  • Selective IgA deficiency
  • IgA and IgG subclass deficiency
  • Autosomal recessive hyper IgM syndromes
  • BCR deficiencies
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9
Q

Describe X-linked agammaglobulinemia. PART 1

A
  • Low immunoglobulins and absent B cells
  • Mutation in Bruton’s tyrosine kinase Btk (encoded by BTK) on X chromosome - in B cell development/maturation
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10
Q

Describe X-linked agammaglobulinemia. PART 2

A
  • Maturation stops at pre-B cell stage - no mature B cells/antibodies
  • Recurrent sinopulmonary infections with encapsulated bacteria
  • Treatment with Ig replacement therapy
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11
Q

Describe CVIDs

A
  • Low IgG and IgA and reduced/normal IgM
  • Normal/low number of B cells
  • Recurrent pulmonary manifestations - pneumonia/asthma/bronchiestasis/pulmonary fibrosis
  • Many patients lead normal lives - receive replacement Ig therapy
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12
Q

Describe selective IgA deficiency.

A
  • Very low IgA in serum
  • Normal IgG and IgM levels
  • Recurrent sinopulmonary disorders, allergies and autoimmune disorders
  • Maturation defect of B cells to produce IgA - cannot develop into IgA-secreting plasma cells
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13
Q

Describe SCID PART 1

A
  • Absence of T cells and/or B cells and NK cells
  • More common in males (X-linked SCID very common)
  • Mutation of gene encoding for common gamma chain in several cytokine receptors i.e those for IL-2/4/7/9/15
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14
Q

Describe SCID PART 2

A
  • Children with SCID usually have severe infections - die during 1st year of life
  • Grafting of viable immunocompetent cells - offers hope of permanent restoration of immune responsiveness
  • Human stem cell transplantation - treatment
  • Tested using TREC test - test for presence of TREC which indicates T cell maturation. Reduced in SCID
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15
Q

Describe DiGeorge syndrome. PART 1

A
  • Arise from defect in thymus embryogenesis
  • Majority - partial monosomy of 22q11.2
  • T cell immunodeficiency - variable expression of disease
15
Q

Describe DiGeorge syndrome. PART 2

A
  • B cells present. T-dependent B cell responses
  • Poorly developed or functioning thymus
  • Underdeveloped parathyroid glands
  • Low set ears, midline facial clefts, congenital heart disorders, delay in development
  • Fatal for children with no T cells - transplantation of stem cells/thymic tissue
16
Q

What are congenital immunodeficiencies caused by?

A
  • Defects in lymphocyte maturation
16
Q

Give examples of defects in innate immunity.

A
  • PHAGOCYTE DEFICIENCIES - example CGD, leucocyte adhesion deficiency
  • COMPLEMENT DEFICIENCY
  • DEFECTS IN NK cells/OTHER LEUCOCYTES - inherited defects in TLR pathways/type 1 interferons
17
Q

Describe CGD. PART 1

A
  • X-linked
  • Severe type of defect in neutrophil function
  • Inability of phagocytes to generate H2O2 - mutations in one of proteins in NADPH oxidase.
  • Microbicidal function impaired - bacteria/ fungi not killed during phagocytosis.
18
Q

Describe CGD. PART 2

A
  • Leads to granuloma formation
  • Severe recurrent infections resulting in pneumonia and skin/bone/organ abscesses
  • Treatment by antibiotics/antifungals
19
Q

Describe complement deficiencies.

A
  • C1q, C4 and C2 deficiency - lupus-like syndrome of flush, glomerulonephritis, fever. C1q deficiency - recurrent pyogenic infections
  • C3 deficiency - present in pneumonia, septicaemia and meningitis
20
Q

What can cause secondary immunodeficiencies? PART 1

A
  • HIV - depletion of CD4+ T helper cells
  • Irradiation/chemotherapy - decreased precursors for leucocytes
  • Involvement of bone marrow by cancers - reduced site of leucocyte development
21
Q

What can cause secondary immunodeficiencies? PART 2

A
  • Protein-calorie malnutrition - metabolic deficiencies inhibit lymphocyte maturation/function
  • Spleen removal - decreased phagocytosis
22
Q

Describe HIV.

A
  • HIV retrovirus synthesise dsDNA - integrate into host genome for viral replication
  • Attacks and destroys T helper cell - attach via CD4 receptor
  • Increased CD8 cells - attack host
  • Susceptible to opportunistic infections
23
Q
A
23
Q

Describe the HIV life cycle.

A
24
Q

Describe the pathogenesis of HIV during acute infection.

A
  • HIV infects CD4+ T cells, migrates to lymphoid tissues
  • Rapid increase in replication as CD4+ T cells are destroyed by virus. Macrophages are also infected.
  • Dendritic cells present antigens and activate HIV-specific CD8+ cytotoxic T cells.
  • Viral load reduces and CD4+ T cells increase.
25
Q

Describe the pathogenesis of HIV during chronic infection.

A
  • CD4+ T cells decline slowly. Viral load remains stable, HIV-specific antibodies are generated
  • Neutralising antibodies begin to appear only after about 3-6 months and HIV replication continues
  • Immune evasion exhausts the immune system leading to opportunistic infection and AIDS

Karan - MBBS Year 1: Respiratory Week 4 (12 decks)

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