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Deja Review-Immuno 9/ Immunodeficiency
Terms in this set (41)
What immune cell deficiency presents with recurrent infections with encapsulated bacteria such as Staphylococcus and Haemophilus influenzae?
What immune cell deficiency presents with recurrent fungal, viral, or protozoal infections?
X-linked hypogammaglobulinemia (Bruton agammaglobulinemia) has low levels of all immunoglobulins due to what underlying deficiency?
Deficiency of B-cell tyrosine kinase receptors, leading to failure of differentiation of pre-B cells to mature B cells
How does Bruton agammaglobulinemia manifest clinically?
Recurrent bacterial infections
Who typically gets Bruton agammaglobulinemia and why?
Young boys due to the X-linked recessive inheritance
How is Bruton agammaglobulinemia treated?
Treat with pooled immunoglobulin (Ig). Mnemonic: Bruton He X-iBITS (exhibits) Immunodeficiency (He = Boys, X-linked, Bacterial infections, Immunoglobulins are low, Tyrosine kinase gene, Six months = start of symptoms)
At what age do most congenital B-cell immunodeficiencies manifest?
About 6 months, as levels of maternal IgG acquired transplacentally during the fetal period begin to fall
What is the most common selective immunoglobulin deficiency, and how do patients present?
Selective IgA deficiency causes recurrent sinus and lung infections (recall IgA is typically present in mucous).
What can occur when patients with selective IgA deficiency receive a blood transfusion?
Anaphylactic reaction if the patients have anti-IgA antibodies that react against IgA in the donor serum
What embryologic process is defective in DiGeorge syndrome?
Development of third and fourth pharyngeal arches, and subsequent aplasia of thymus (third arch) and parathyroids (third arch: inferior parathyroids, fourth arch: superior parathyroid)
What immune deficiency is part of DiGeorge syndrome and how is it treated?
Deficit of T cells due to thymic aplasia results in fungal, viral, and protozoal infections (eg, Pneumocystis pneumonia [PCP] and Candida albicans). Treat with fetal thymic transplant.
What electrolyte disturbance is seen in DiGeorge syndrome?
Hypocalcemia (and tetany) due to failure of parathyroid development
Mnemonic: DiGeorge syndrome affects TWO arches (3 and 4), TWO organs (thymus and parathyroid), and has TWO defects (defective T cells and hypocalcemia).
What are the clinical and laboratory manifestations of hyper-IgM syndrome?
Clinical: recurrent pyogenic bacterial infections early in life
Laboratory: see high IgM, but low IgG, IgA, IgE
What is the underlying genetic defect in hyperIgM syndrome?
A mutation in CD40 ligand gene leads to a defective CD40L on T-cell surfaces. Without the proper CD40L-CD40 signaling, B cells cannot switch isotypes from IgM to other classes.
Mnemonic: Hyper-IgM Alphabet: A... HIJK_MMMMMM . . . Z (No L = CD40 Ligand and a lot of IgM)
To what infections are patients with interleukin 12 (IL-12) receptor deficiency predisposed?
Disseminated mycobacterial infections, because IL-12 is involved in development of the cell-mediated Th1 response against mycobacteria
What types of immune cells are defective in severe combined immunodeficiency disease (SCID) and how is it inherited?
B and T cells. Most cases (75%) are X-
How does SCID clinically manifest and how is it treated?
Patients are predisposed to recurrent bacterial, viral, fungal, and protozoal infections. Treat with bone marrow transplant.
What defects can lead to SCID?
Most common, about 50%, is the lack of the common γ chain of the IL-2, IL-4, IL-7, and IL-15 receptors (needed for T-cell de- velopment). The next most common, about 16%, is an adenosine deaminase (ADA) deficiency required for the purine salvage pathway.
How is Wiskott-Aldrich syndrome inherited and how does it present?
X-linked recessive. It presents with pyogenic infections, eczema, and bleeding due to thrombocytopenia.
What is the major defect in Wiskott-Aldrich syndrome and how is it treated?
Lack of an IgM response to bacterial capsules. Treat with bone marrow transplant. Mnemonic:
1. Turn the W in Wiskott upside down: W→IgM
2. X-PECT (Expect) infections with Wiskott- Aldrich (X-linked, Pyogenic infections, Capsular response impaired, Thrombocytopenia)
What cancer are patients with Wiskott-Aldrich syndrome prone to develop?
How does ataxia-telangiectasia present?
Patients have recurrent infections at a young age in addition to uncoordinated gait (ataxia) and skin lesions consisting of small, dilated terminal vessels (telangiectasias)
How is ataxia-telangiectasia inherited and what is the genetic defect?
Autosomal recessive mutation in DNA repair enzymes
What immunoglobulin deficiency is often seen with ataxia-telangiectasia?
What is the genetic defect in chronic granulomatous disease (CGD) and how is it inherited?
Lack of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Usually X-linked recessive
What is the function of NADPH oxidase and in what cells is it found?
NADPH oxidase helps generate H2O2 used in respiratory bursts of neutrophils.
What are the principal sources of infection in chronic CGD and the most common cause of death
Fungal and bacterial infections. Pneumonia due to Aspergillus fumigatus is the most common cause of death from chronic CGD.
What bacteria typically infect patients with CGD?
Catalase-positive bacteria (Staphylococcus aureus and Escherichia mil) that use catalase to degrade their endogenous H2O2. Burkholderia cepacia is the most common bacterial cause of death in CGD.
What bacteria can CGD patients resist?
Catalase-negative bacteria (Streptococcus pyogenes) that cannot degrade their endogenous H2O2, which is then utilized by neutrophils. The bacteria provide the bullet!
Chédiak-Higashi syndrome is due to a microtubule dysfunction, and presents with recurrent pyogenic infections. What are the two abnormalities seen in the immune cells of these patients?
1. Failure of lysosome/phagosome fusion → large granular inclusions of abnormal lysosomes
2. Abnormal neutrophil chemotaxis
What are the features of Job syndrome (hyper-IgE syndrome)?
High IgE, recurrent cold staphylococcal abscesses, eczema, and skeletal abnormalities
What is the underlying deficiency in Job syndrome?
Lack of γ-interferon (γ-IFN) production by Th1 cells (inflammatory cells)
What is a cold abscess?
Low γ-IFN favors the development of Th2 cells that are anti-inflammatory (and the source of IL-4 that induces B-cell production of IgE). Therefore, staphylococcal abscesses cannot trigger the hot or inflammatory response.
Mnemonic: GEt an EASy Job (Gamma- IFN, IgE, Eczema, Abscesses, Skeletal abnormalities)
What is leukocyte adhesion deficiency syndrome? How does it present?
Autosomal recessive defect of lymphocyte functionassociated 1 (LFA-1), an adhesion protein on leukocytes, leads to severe pyogenic infections.
Common variable immunodeficiency presents with recurrent pyogenic infections. What is the underlying cause of this disorder?
Hypogammaglobulinemia due to a block in B-cell differentiation to plasma cells
What immune cells are most affected in human immunodeficiency virus/acquired im- munodeficiency syndrome (HIV/AIDS) and what types of immunity are compromised?
HIV targets CD4+ helper T cells which results in dysfunction of both humoral and cell-mediated immunities.
What are some examples of bacterial infections that are common in AIDS patients?
Mycobacterium tuberculosis, Mycobacterium avium-complex, Streptococcus pneumoniae (most common case of pneumonia in AIDS patients, not PCP), Salmonella, etc.
What are some examples of viral infections that are common in AIDS patients?
Cytomegalovirus, papovavirus, JC virus, herpes simplex virus type 1 (HSV-1),
varicella-zoster virus (VZV), Epstein-Barr virus (EBV)
What are some examples of fungal infections that are common in AIDS patients?
Cryptococcus, Candida, Histoplasma, Mucor, Pneumocystis jiraveci (formerly Pneumocystis carinii), Coccidioides, Blastomyces, etc.
What are some examples of protozoal infections that are common in AIDS patients?
Cryptosporidium, Toxoplasma, etc.
AIDS patients are at increased risk for what malignancies?
Kaposi sarcoma, Anal carcinoma, Non- Hodgkin lymphoma, and Cervical cancer Mnemonic: (KANCer)
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