MLT GlobeImmunology & Serology: Autoimmune & hypersensitivity – page 2
80 Immunology & Serology MCQs on Autoimmune & hypersensitivity with answers and explanations.
Which autoantibody is found in most patients with generalised myasthenia gravis?
About 85% of generalised myasthenia gravis have antibodies that block or destroy acetylcholine receptors. Anti-VGCC is linked to Lambert–Eaton syndrome and anti-aquaporin-4 to neuromyelitis optica.
Rheumatoid factor detected by latex agglutination is usually an antibody of which class directed against which target?
Classic RF is IgM directed against the Fc portion of IgG. Latex particles coated with human IgG are agglutinated by IgM RF.
A tuberculin skin test that becomes indurated 48–72 hours after injection is an example of:
Delayed-type (type IV) hypersensitivity is mediated by sensitised T cells and macrophages, not antibody, and peaks at 48–72 hours. Contact dermatitis is another example.
Anti-smooth muscle antibodies with F-actin specificity are most associated with:
ASMA (anti-F-actin) and ANA are the serologic markers of type 1 autoimmune hepatitis. Type 2 disease is marked by anti-LKM-1, and primary biliary cholangitis by antimitochondrial antibody.
A 40-year-old woman has a firm goitre, fatigue and raised TSH. Which antibody is found in most patients with this likely condition?
Hypothyroidism with goitre suggests Hashimoto thyroiditis, in which anti-TPO antibodies are present in about 90% of patients. TSH receptor stimulating antibodies cause Graves hyperthyroidism, not hypothyroidism.
Antibodies to glutamic acid decarboxylase (GAD65) are most useful to support a diagnosis of:
GAD65 antibodies, with insulin, IA-2 and ZnT8 antibodies, mark autoimmune beta-cell destruction in type 1 diabetes and latent autoimmune diabetes of adults. They are not typical of insulin-resistant type 2 diabetes.
A woman has dry eyes, dry mouth and parotid swelling. Anti-SS-A (Ro) is positive. Which additional antibody is most characteristic of this condition?
Anti-SS-A and anti-SS-B are the classic antibodies of Sjögren disease; anti-SS-B rarely occurs without anti-SS-A. Anti-Scl-70 is associated with diffuse systemic sclerosis.
To identify the allergen responsible for hay fever without skin testing, the laboratory should measure:
In vitro allergen-specific IgE immunoassays identify sensitisation to individual allergens and replace skin prick testing when needed. Total IgG or allergen IgG4 does not identify IgE-mediated allergy.
A jeweller develops an itchy eczematous rash where a nickel bracelet touches her skin. A patch test is read at 48–96 hours. The mechanism is:
Allergic contact dermatitis is delayed-type (type IV) hypersensitivity: sensitised T cells react to hapten-protein complexes over 48–96 hours. IgE-mediated reactions appear within minutes.
A group A patient receives group B red cells in error and develops fever, back pain and haemoglobinuria. Which hypersensitivity type is this?
Preformed anti-B binds antigen on transfused red cells, activates complement and causes intravascular lysis – an antibody against a cell-surface antigen, i.e., type II. Type III involves soluble immune complexes.
Which method is considered the reference screening method for antinuclear antibodies?
Indirect immunofluorescence on HEp-2 cells detects a wide range of nuclear and cytoplasmic antibodies and gives pattern information. Immunodiffusion detects only selected ENA specificities and is less sensitive.
Rheumatic heart disease after group A streptococcal pharyngitis arises because antibodies to streptococcal M protein also bind cardiac tissue. This mechanism is called:
In molecular mimicry, a microbial antigen resembles a self antigen, so the immune response cross-reacts with host tissue. Immune privilege describes sites where immune responses are limited.
Celiac disease is an immune-mediated reaction triggered by which dietary component?
In celiac disease, gliadin from gluten in wheat, barley and rye triggers an immune response that damages the small-intestinal villi. Lactose intolerance is an enzyme deficiency, not an autoimmune disease.
The antinuclear antibody (ANA) test is used mainly as a screening test for:
A negative ANA makes SLE very unlikely, so it is the main screening test. Positive results are followed by tests for specific antibodies such as anti-dsDNA and anti-Sm.
Autoimmune hemolytic anemia, in which antibodies bind the patient's red cells, is which type of hypersensitivity?
In type II reactions antibody binds antigen on cell surfaces, leading to complement activation or phagocytosis of the cells, as in autoimmune hemolytic anemia.
Systemic lupus erythematosus occurs most often in:
SLE is about nine times more common in women than men and usually starts between puberty and menopause.
A raised total serum IgE is most commonly associated with:
IgE mediates type I hypersensitivity, and total IgE is often raised in atopic conditions such as allergic asthma and eczema, as well as in helminth infections.
The LE cell, described in early lupus testing, is a neutrophil that has engulfed:
An LE cell is a phagocyte that has ingested nuclear material opsonised by antinuclear antibody. It has been replaced by ANA testing but explains the history of lupus serology.
Multiple sclerosis is an autoimmune disease that damages:
In multiple sclerosis, immune attack on central nervous system myelin causes demyelinating plaques. CSF often shows oligoclonal IgG bands.
In pemphigus vulgaris, autoantibodies attack which structure in the skin?
Pemphigus antibodies target desmogleins, causing loss of adhesion between epidermal cells and fragile intraepidermal blisters. Bullous pemphigoid targets hemidesmosomes.