MMSC415 Exam 2

What are the five types of vaccines?

- Killed microorganisms or inactivated viruses --> Killed with heat, chemical treatment, or radiation; Downside: incomplete inactivation can cause disease when introduced into the patient

- Live attenuated vaccines --> Mutant form of live pathogen that grows poorly in human cells or is no longer pathogenic; Downside: can convert to wild type and infect people or revert to pathogenic form and spread to others; Attenuated by growing the virus in another species so it will become specialized for those cells; attenuated = weakened

- Subunit vaccines --> Purified single or mixed components; ex. Proteins and polysaccharides → pick the most immunogenic components of pathogens; Ex. toxoids (inactivated toxins) like diphtheria and tetanus; acellular pertussis (toxin + protein)

- Conjugate vaccines --> Protein-polysaccharide complex; Sometimes polysaccharides don't activate T cells so linking it to a protein will ensure T cell activation so they can form memory cells

- Recombinant vaccines --> Gene cloned into another microorganism in vitro; Process: 1. Identify the target subunit 2. Isolate gene and transfer into bacteria or yeast 3. Culture them and harvest 4. Extract and purify subunit

Difference between immediate and delayed hypersensitivity reactions

- Immediate --> antibody mediated; occurs within seconds to hours of second contact with allergen; Types I-III

- Delayed --> cell-mediated; >12 hours, max 48-72 hours; type IV

Type I hypersensitivity

- allergen elicits an IgE antibody response upon sensitization

- Exposed to allergen, activation of antigen-specific Th2 cells, Th2 cells activate B cells to secrete IgE, mast cells and circulating basophils and eosinophils bind allergen specific IgE via the Fc portion to their surface using receptors, cells (majority mast cells) are now armed to recognize a secondary exposure

What do mast cells and basophils contain in their granules

histamine, heparin, proteases

Early vs late phage type I hypersensitivity

- Early: mast cells

- Late: eosinophils

Examples of type I hypersensitivity

Asthma, dermatitis, hives, angioedema

Diagnosis for Type I hypersensitivity

- intradermal testing

- Radioallergosorbent test (RAST) --> tests for antigen specific IgE

- Radioimmunosorbent test (RIST) --> measures total serum IgE

- food elimination diet

- oral food challenges

Treatment for type I hypersensitivity

- avoid allergens

- immunotherapy --> allergy shots to desensitize immune system and hopefully develop tolerance

- treat symptoms

Type II hypersensitivity

- cytotoxic

- Self reactive B and T cells escape positive and negative selection → reactive to intrinsic antigens

- Ex. drug induced → 1. Penicillin binds to cell surface receptor causing it to appear as foreign 2. B cell encounters the antigen, internalizes it, and starts producing antibodies against it with the help of a T cell 3. Antibodies are produced (IgM or IgG) 4. Antibodies bind to the epitope and opsonization with complement components occurs and lysis is attempted via MAC complex 5. Antibody-dependent cell mediated cytotoxicity via NK cells, macrophages, neutrophils, and eosinophils calling

Examples of Type II hypersensitivity reactions

- acute hemolytic transfusion reactions

- hemolytic disease of the newborn

- drug induced hemolytic anemia

- myasthenia gravis

Type III hypersensitivity

- immune complex

- Occurs through the deposition of circulating immune complexes (antigen-antibody complexes) in tissues; accumulate in the skin, joints, blood vessel walls, lung alveoli, and kidney glomeruli

- Immune complexes are usually cleared by monocyte-macrophage system but small complexes are not as attractive and may continue to circulate and then deposit in various tissues

- PMNS attempt to phagocytize immune complexes that are bound to tissues but they can't so they degranulate and release toxic granules leading to tissue damage

Examples of type III hypersensitivitiy

- arthus reaction

- serum sickness

- rheumatoid arthritis

- SLE

- farmers lung

Type IV hypersensitivity reaction

- DTH --> delayed-type hypersensitivity

- T cells

- 1. Initiated by CD4+ T cells when they recognize and bind foreign antigen presented with MHCII by APCs → APC secretes IL-12 causing TH0 cells to differentiate into TH1 cells 2. TH1 cells secrete IL-2 causing proliferation and IFN-y recruits secondary cells like macrophages, neutrophils, and other T cels 3. Phagocytes release proinflammatory cytokines and degranulation causes cellular tissue damage

- Antigens inside cells are presented with MHCI to CTLs which kills target cells with perforins and granzymes

Examples of Type IV hypersensitivity

- granulomatous

- TB skin test

- contact dermatitis

B cell deficiencies

- absent, low in numbers, decreased Ab production, heavy or light chain deficiencies, altered function

- X-linked agammaglobulinemia → defect in tyrosine kinase does not allow B cells to mature; low levels of B cells and plasma cells and low/abcense of antibodies

- Selective IgA deficiency → most common primary antibody deficiency as no class switching is occurring; common to have recurrent upper respiratory tract infections

T cell deficiencies

- T cells → absent, low in numbers, altered function

- X-linked hyper IgM syndrome → defect in CD40L on T cells; high levels of IgM and low levels of IgG, IgA, and IgE

- Wiskott-Aldrich Syndrome → WAS gene mutation leads to nonfunctional WAS protein; loss of/impairment of cell signaling and actin cytoskeleton function, causing immunodeficiency, thrombocytopenia (low platelet count), and eczema

- DiGeorge syndrome → thymus fails to develop so T cells are affected

- Adenosine deaminase deficiency (ADA) → purine degradation leading to the accumulation of toxic deoxyadenosine in human cells which is toxic for developing T cells

Wiskott-Aldrich Syndrome

Type of T cell immunodeficiency --> WAS gene mutation leads to nonfunctional WAS protein; loss of/impairment of cell signaling and actin cytoskeleton function, causing immunodeficiency, thrombocytopenia (low platelet count), and eczema

Severe combined immunodeficiency (SCID)

family of disorders resulting from a defect in lymphocyte development that alters either T cells or T and B cells

Example of a disease that arises from the immunodeficiency of phagocytic cells

Chronic granulomatous disease: defective NADPH oxidase → no ROS, meaning neutrophils can engulf but not destroy

Types of immunodeficiencies

B cell, T cell, SCID, complement, phagocytic cell, ataxia-telangiectasia

Complement immunodeficiency

- decreases immune complex clearance

- Deficiency of C1 inhibitor produces hereditary angioedema → inhibits the activation of the C1 complex, producing an uncontrolled classical pathway leading to episodes of swelling, predominantly in the face

Ataxia-telangiectasia

- ataxia = poor coordination, telangiectasia = small dilated blood vessels

- Mutations in ATM gene lead to inadequate/no response to DNA double-strand breaks

- Immunodeficiency in developing lymphocytes and impaired VDJ recombination

ELISA

Detect extractable nuclear antigens (ENAs)

ANA trends based on immunodeficiency

- homogeneous --> SLE

- systemic sclerosis --> centromere

- Sjogren's syndrome --> speckled

What are the possible ANA trends?

homogeneous, speckled, nucleolar, nuclear membrane/peripheral, centromere

what is autoimmunity

loss of self tolerance

what hypersensitivity reactions to autoimmune diseases resemble

- type II, III, and IV

- type II --> autoantibodies to host cell surface or extracellular matrix

- type III --> soluble immune complexes deposit in tissues

- type IV --> autoimmunity caused by effector T cells

Systemic lupus erythematosus pathology

Increased TH cells and decreased Treg cell function, overreactive B cells, immune complexes are formed and not cleared, and circulating autoantibodies (IgG) to specific cellular components common to many different cell types

Systemic lupus erythematosus diagnosis/serology

antinuclear antibodies (ANA), anti-dsDNA antibodies, anti-smith antibodies, low complement levels

Systemic Sclerosis

- increased collagen (structural protein in skin and other connective tissues) production, deposited in skin and other organs

- centromere ANA pattern

Sjogren's syndrome

- autoimmune disorder against lacrimal and salivary glands leading to dry mouth and eyes

- speckled ANA pattern

Rheumatoid Arthritis pathogenesis

stimulation of B cells that make IgM, IgG, or IgA against the Fc region of IgG and these autoantibodies are called Rheumatoid factor

Rheumatoid Arthritis diagnosis

- Rheumatoid factor

- anti-CCP

multiple sclerosis pathogenesis

- activated T cells surmount the blood-brain barrier to secrete cytokines

- EBV mimics myelin basic protein in the myelin sheath via molecular mimicry

Myasthenia gravis pathogenesis

neuromuscular junction releases acetylcholine which binds to acetylcholine receptor → autoantibodies to AChR

Diabetes Mellitus (Type I) pathogenesis

selective destruction of the insulin-producing beta cells in the pancreas; hypothesis is that T cells lose tolerance to beta cells, THi cells develop and trigger CMI response; autoantibodies are present but do not seem to play a role in the damage

Autoimmune thyroid diseases

- Hashimoto thyroiditis --> autoantibodies and TH17 cells specific for thyroid antigens; thyroperoxidase antibodies (anti-TPO); formation of a goiter, hypothyroidism caused by binding of antibodies that interfere with the production of thyroid hormones

- Graves disease --> autoantibodies to thyroid-stimulating hormone receptor cause thyroid stimulation → hyperthyroidism

Ankylosing Spondylitis

chronic inflammation of the spine beginning in the sacroiliac joint

Risk factor of Ankylosing Spondylitis

HLA-B27

Goodpasture syndrome

anti-glomerular basement membrane disease affecting the kidneys and lungs; Anti-GBM antibodies

Autimmune hemolytic anemias

- Cold agglutinin disease (CAD) → IgM to human RBC I antigen

- Paroxysmal cold hemoglobinuria (PCH) → IgG coats RBCs at cold temp and fixes complement, but lysis of RBC occurs upon return to 37℃

- Warm autoimmune hemolytic anemia → IgG coats RBCs at 37℃ and cells are lysed

Multiple myeloma

- proliferation of a single B cell clone, monoclonal gammopathy

- Bence jones proteins: secreted free light chains; detained in blood and urine and are a diagnostic

Diagnosis of multiple myeloma

CRAB:

- C --> hypercalcemia

- R --> renal insufficiency

- A --> anemia

- B --> bone lesions

Waldenstrom's macroglobulinemia

form of non-Hodgkin lymphoma; high levels of circulating monoclonal IgM; causes many symptoms due to hyper viscosity syndrome

Types of grafts

- Xenograft: translation from one specific to a different species

- Allograft: transplantation from one individual to a genetically non-identical recipient (most common)

- Isograft: transplantation from one individual to a genetically identical recipient

- Autograft: transplantation from one site of an individual to another site of the same individual

Histocompatibility

determined by the compatibility of HLA genes; for solid organs you want to match ABO blood group and as many HLAs as possible (MHC-I and MHC-II are important); molecular HLA typing

Graft vs. host disease

- seen in bone marrow and stem cell transplants

- Graft attacks recipient cells and tissues systemically

What does development of graft vs host disease require

histoincompatibility, immunocompetent donor T cells, and an immunosuppressed or immunodeficient host

Tumor (immune) surveillance

theory of Paul Ehrlich; tumor cells typically possess weak immunogens and decreased expression of MHC/HLA antigens

What are the steps of immunoediting

- Elimination: innate and adaptive immune responses detect and destroy tumor cells

- Equilibrium: tumor cells are not completely eradicated, selective pressure exerted by immune cells

- Escape: tumor cells can spread to other sites and lead to clinically apparent disease

Tumor markers (antigens)

- Alpha-fetoprotein (AFP): major plasma protein produced by fetal liver/yolk sac, stops by birth; AFP-secreting tumors seen in hepatocellular carcinoma as tumors of the liver revert to old form and make abnormal antigens; elevated serum AFP

- Carcinoembryonic antigen (CEA): glycoprotein involved in cell adhesion; produced in GI tract of fetus and stops before birth; CEA-secreting tumors seen in colorectal carcinoma; elevated serum CEA

- Prostate-specific antigen (PSA): secreted by prostate gland; elevated in prostate cancer; used for screening but not for definite diagnosis

- Human chorionic gonadotropin (hCG): hormone secreted by trophoblast cells surrounding embryo; hCG secreting-tumors seen in testicular cancer

- Cancer antigens help monitor patients undergoing treatment: CA-125 → ovarian cancer; CA19-9 → pancreatic cancer

What prevents graft vs host disease

irradiation → killing of lymphocytes in the blood

Prozone effect

antibody excess

Post zone effect

antigen excess

Turbidimetry

the measurement of light transmitted through a suspension of particles; measures turbidity or cloudiness of solution

Nephelometry

a direct measurement of light scattered by particles suspended in solution

What is the second step of agglutination reactions

lattice formation

Passive agglutination

carrier particle coated with Ag not normally present; ex. Latex agglutination to detect Ab

Reverse passive agglutination

Ab attached to a carrier particle facing outward; ex. Latex agglutination to detect Ag

hemagglutination inhibition

some viruses naturally agglutinate RBCs; mix patient serum with viral suspension and then add the RBCs the virus is known to agglutinate; no agglutination means the patient serum had antibodies specific to the virus, which prevented hemagglutination

What are the different labels used in labeled antibody tests

fluorescent (uses fluorochromes, ex. Fluorescein, isothiocyanate), enzyme, chemiluminescent, and radioactive

What does a direct fluorescent antibody (DFA) test for

detect antigens in tissue, sample, or cell suspension on a slide using an antigen-specific fluorescently labeled Ab

What is added to the solid phase antigen in a DFA

Solid phase antigen on a slide + labeled antibody conjugate (antibody coupled with fluorochrome) → antigen-antibody combination fluorescence

Indirect fluorescent antibody (IFA) test

detect unlabeled, primary patient antibody in sample using fluorescent-labeled secondary antibody

What is added to the solid phase antigen in an IFA

Solid phase antigen on slide + unlabeled antibody (patient serum) → antigen antibody combination + labeled anti-immunoglobulin conjugate → fluorescence

What does a capture/sandwich immunoassay detect

antigens or antibodies

Competitive immunoassay for antibody results

signal detected inversely proportional to antibody concentration

What does ELISA stand for

Enzyme-linked imunosorbent assay

What are cells in a fluorescence-activated cell sorting stained with

fluorescently labeled antibodies

what does LASER in fluorescence-activated cell sorting stand for

light-amplified stimulated emitted radiation

What does EIA stand for

enzyme immunoassay

What do you incubate patient sample with in the enzyme-multiplied immunoassay technique (EMIT)

anti-drug Ab

What does Streptavidin-biotin labeling do

amplifies signal

What does RAST stand for

radioallergosorbent test

What does RAST measure

allergen-specific IgE

What is Western Blotting

- Electrophoretically separate subspecies of antigens (proteins) and transfer them to a membrane

- Add patient serum with antibodies to specific epitopes of separated antigens

- Detect antibodies by using labeled anti-human antibodies

- Visualize color development enzymatically or by chemiluminescence

What does western blotting detect

Detect antibodies by using labeled anti-human antibodies

What does complement fixation test detect

specific antibody

What is used as a reagent in the complement fixation test

complement

What do results of a complement fixation test look like

if hemolysis present (pink) test is negative, but if no hemolysis (RBC pellet) test is positive

What is a primary lesion in syphilis called

chancre

Describe a flocculation reaction for syphilis testing

IgG or IgM to lipids released from damaged host cells during infection; looking for antibodies indicating inflammatory process not against pathogen;

What are treponemal tests used for

confirmation of reactive RPR or VDRL

What should you do if there is blood present in a cerebrospinal fluid test for neurosyphilis

reject the sample

What is the main concern with using live-attenuated vaccines?

Viruses may revert to their pathogenic form

What is the main concern with using subunit vaccines

Purified antigens may not be immunogenic

What is the main concern with using killed/inactivated vaccines

Viruses may not be completely inactivated

What is an example of a complement deficiency?

hereditary angioedema

How could you test for FUNCTIONAL humoral-mediated immunity?

vaccinate the patient and then later test for antibody titer

Which of the following may result in a severe combined immunodeficiency?

a. DiGeorge syndrome

b. X-linked agammaglobulinemia (XLA)

c. Adenosine deaminase (ADA) deficiency

A and C

a. DiGeorge syndrome → lack of T cells because the thymus is underdeveloped

b. X-linked agammaglobulinemia (XLA)

c. Adenosine deaminase (ADA) deficiency → toxic buildup of adenosine byproducts in T cells causing death

How should serum be stored if testing will be delayed?

short-term refrigerated, long-term frozen

T/F - Hemolysis in a complement fixation test is a positive result

False - complement is available to fix RBCs if the antibody is NOT present

What is being detected in a Western blot or dot blot?

specific antibodies in a patient sample

What is molecular mimicry

structural similarities between a microorganism's antigens and our self-antigens