Immunodeficiency Flashcards
Secondary immunodeficiency diseases arise from
Infection with agents that deplete immune cells, malnutrition or treatments with immunosuppressive drugs.
Antibody deficiency is due to…
B cell problems or facts in T cells affecting maturation of B cells
Combined immunodeficiencies affect
Both B and T cells
Phagocytes cell disorders affect
Granule yet and macrophages
Complement deficiencies affect
Function or regulatory components of the complement system
Immune regulation is when
Influencing mechanisms are designed to control autoimmune disease, apoptosis or immune pathology
Primary immunodeficiency diseases arise from?
Intrinsic defects in cells and mediators of the innate and adaptive immune system
The outcome of antibody deficiency is
Pus forming pyogenic infections. Incl. H. influenzae, S. pneumoniae, S. aureus
Outcome of combined immunodeficiency is…
Infection by bacteria, viruses & opportunistic pathogens
Neutrophil immunodeficiency leads to….
Bacterial and fungal infections
Macrophage immunodeficiency leads to…
Mycobacterial diseases - they replicate in phagosomes of macrophages. There is an inability to clear mycobacterium when macrophages become affected
Toll-like receptor immunodeficiency leads to
Infection with TLR specific pathogens
Complement immunodeficiency leads to…
Pyogenic infections. Deficiencies can also increase susceptibility to autoimmune diseases (i.e. SLE) because, complement is a way of clearing apoptotic bodies from the blood stream. If complement doesn’t work, the DNA and his tones can cause links to systemic lupus.
What does XLA stand for?
Congenital agammaglobulinamia (X-linked)
What mutation causes XLA and what phenotype does it cause?
Mutation at the Bruntons tyrosine kinase (btk) gene that leads to a severe block in B cell development (at the pre-B to immature B cell stage)
What other gene mutation gives rise to a similar phenotype?
Mutation in the adaptor protein BLNK but 80-90% of affected with XLA have mutations in BTK
XLA children symptoms:
Lack IgA, M, D & E and have low IgG. Virtually no circulating B cells. No tonsils and tiny lymph nodes.
Why do XLA children survive normally for the first 6 months?
Protection from maternal immunoglobulins
How do you treat children with XLA?
Regular IgG injections
How does IgA deficiency arise?
IgA secreting B cells are unable to differentiate
Hyper IgM leads to…
No IgG, IgA, IgE
Common Variable Immune Deficiency (CVID) has what effect on Ig secretion
Affects differentiation of most plasma cells but get IgM from immature B cells.
What is the most common immunodeficiency?
CVID 1:10000
A common pathology seen in hyper IgM syndrome is
Lymph node with no germinal centres
Patients with CVID are at high risk of
Autoimmune complications, granulatomous lesions, lymphoid hyperplasia, lymphoma
Giardia lamblia is a normally copable pathogen, when and where can it cause infection?
Infection in the GI tract due to a lack of IgA
What leads to hyper IgM syndrome?
CD40L deficiency. CD40L activates B cells (by T cells). This activation is required for class switch and formation of germinal centres where extensive B cell proliferation occurs.
Severe combined immunodeficiency (SCID) affects which immune cells
T cells
Adenosine deaminase and purine nucleoside phosphorylase affects what pathway that leads to SCID?
Thymocytes survival pathway
JAK3 and IL-7R genes when affected lead to what pathway being affected in SCID?
Lymphoid progenitor expansion
RAG1 or RAG2 genes affect what pathway in SCID?
Pre-T cell receptor
Pre-TCR signalling pathway is affected by which genes to lead to SCID?
CD3 and CD45
Positive selection of T cells is affected by what genes to cause SCID?
HLA class II & ZAP-70 (one of the early signalling molecules in T cell activation)
The calcium signalling pathway is affected by what genes to lead to SCID?
Stim 1 and Orai 1
Where is thymic epithelium derived from?
3rd and 4th pharyngeal pouches at 6 weeks gestation
What is the DiGeorge anomaly?
Congenital defects in organs derived from the 3rd and 4th pharyngeal pouches. Including the face and the heart.
What do Fas and FasL control?
Lymphocyte homeostasis
What disorders do defects in Fas and FasL give rise to?
Fas: Lpr mouse & ALPS type 1a in man FasL: Gld mouse & ALPS type 1b in man
FoxP3 is what to Treg cells?
A master gene
Where is the AIRE gene expressed and what does it control?
In the thymus and controls expression of self antigens. It leads to the deletion of self reactive cells.
What happens if AIRE is mutated?
Self reactive cells are able to leave the thymus leading to APECED (autoimmune polyendocrinopathy candidiasis ectodermal dystrophy.
Two diseases that arise due to defects in phagocytes are
Chronic granulatomous disease and leukocyte adhesion deficiency
What is the reaction for the breakdown of NADPH and the enzyme that carries out the reaction?
NADPH + 2O2 -> NADP+ + 2O2- + H+ NADPH oxidase
Why is the oxidation of NADPH so important in phagocytes?
It produces superoxide anions which are antibacterial and this can generate hydrogen peroxide which combined are very important for control of infection in phagosomes of WBCs
What disease arises due to defective NADPH oxidaseB
CGD
Without NADPH oxidase, patients with CGD have an inability to……….. Which leads to…….. Children with CGD develop………
- Clear infection 2. Leads to granule a formation 3. Pneumonia, LN infections and abscesses in skin and live etc.
Type I LAD develops as a result of what?
CD18 defects which forms a major chain of a family of integrins including LFA-1 and CR3. Defects in CD18 prevents the cells from adhering to the vascular endothelial wall. Defects in CR3 also affects binding to opsonised bacteria via C4bi receptor.
Type II LAD occurs as a result of what?
Sialyl Lewis (sugar expressed on CD15) is dysfunctional because of a defect in a fucose transporter. SLX is required for leukocyte adhesion via E-selectin in the tethering stage of leukocyte adhesion.
What group of genetic complement deficiencies is autosomal dominant and what is it a deficiency in?
group II, causes angioedema by a C1 inhibitor deficiency
Why do Group I genetic complement deficiencies cause immune complex disease and what factors cause the effects? What type of genetic disease are they?
C1q, C1s (or C1r and C1s), C2, C4 These all reduce the size of an immune complex. Autosomal recessive.
Recurrent pyogenic infections occur in group III genetic complement disorders, what factors and involved and why do they have this effect?
C3, factor H, factor I. These factors cause pyogenic infections because, all are early triggers in both the classical and alternative complement pathways (C3 is the first trigger in both pathways). They promotes bacterial opsonisation and take up of bacteria by neutrophils and phagocytes.
Deficiencies in C9 complement causes what type of defect?
Asymptomatic
Are genes and mutations involved in secondary immunodeficiencies?
No.
How do infection and malnutrition affect each other?
They interrelate and promote each other. Malnutrition = depletion of protein-energy reserves and decreased immunity. Infection = decreased absorption, increased catabolism, decreased intake via anorexia, nausea and vomiting and increased nutrient from urine and faeces.
When are immunosuppressive drugs likely to be given?
For long periods after solid organ or bone marrow transplant
What are glucocorticoids used for?
To treat allergy symptoms and autoimmune conditions.
What interleukins do Glucocorticoids reduce?
IL-1, IL-6, IL-8 and IL-12 secretion
Glucocorticoids suppress:
Prostaglandin, COX2 synthesis and mast cell degranulation as well as, MHC II , CD80 & CD86 expression by APC’s. This blunts the innate and adaptive immune responses.
What are the 5 evolved components of natural immunity
Physical barriers, phagocytosis, lectins, enzymes, NK cells
What are the 5 factors of acquired immunity?
Antibodies, lymphocytes, antibody receptors, lymph nodes, regulation
Immunoglobulins and TCRs equip mammals with the capacity for…
Acquired immunity to antigens
What enzyme adds bases to the J region as antibodies are generated?
Terminal nucleotide transferase
What is immunological tolerance?
There is central tolerance and peripheral tolerance as well as self-tolerance ( a number of mechanisms that protect the individual from self reactive lymphocytes).
What is the difference in affinity maturation of B and T cells?
T cells do not undergo somatic hypermutation in the TCR genes.
When T cells enter the thymus they have no TCR or CD4 or CD8, what is this called in terms of CD molecules?
Double negative
What is the pre-Talpha
A molecule that mimics the TCR alpha chain and binds the beta chain. It selects for a beta chain that will bind and fold correctly. Once a beta chain has been selected for the TCR alpha chain can be selected.
What does the pre-Talpha chain signal?
Allelic exclusion where beta chain expression from one chromosome prevents beta chain expression off of the other chromosome. This is not the case for the the alpha chain, meaning you can get two alpha chains being expressed.
Why do 98% of all thy oxygen die by apoptosis?
Because firstly they do not have a TCR that is able to interact with MHC or because of negative selection and their MHC receptor has high affinity for self MHC or (self MHC + self antigen) on an APC such as a macrophage or a DC. Also if there are cells with higher affinity the T cells are not selected.
Where does negative selection occur?
Mainly on the medullary dendritic cells and macrophages.