lOMoAR cPSD| 67691079
Hypersensitivity Reactions and Hematologic Disorders Study Guide
Hypersensitivity: Type 1 Allergic Reaction Mediated by IgE
• Inflammation due to mast cell degranulation
• Local symptoms: itching, rash
• Systemic symptoms: wheezing
• Most dangerous form is an anaphylactic reaction-systemic response-hypotension,
severe bronchoconstriction, tx: epinephrine reverses the effects
Hypersensitivity: Type 2 Cytotoxic Reaction; Tissue Specific (thyroid)
• Macrophages are the primary effectors cells involved
• Can cause tissue damage or alter function
• Grave’s disease (hyperthyroidism)-example of altering thyroid function, but does not
destroy thyroid tissue
• Incompatible blood type: example of cell/tissue damage that occurs; severe transfusion
reaction occurs, transfused erythrocytes are destroyed by agglutination or
complementmediated lysis
Difference Between Type 2 and Type 3
• Type 2 is organ specific; the antibody binds to the antigen on the cell surface
• Type 3 is not organ specific; the antibody binds to soluble antigen outside the cell
surface that was released into the blood or body fluids, and the complex is then
deposited in the tissues
Hypersensitivity: Type 3
Examples
• Rheumatoid Arthritis: Antigen/antibodies are deposited in the joints
• Systemic Lupus Erythematosus (SLE): Antigen/antibodies deposit in organs that cause
tissue damage
• Scope of Damage of SLE-Type 3-autoimmune response (Lupus): Facial rash confined to
the cheeks (malar rash), Discoid rash (raised patches, scaling), Photosensitivity (skin
rash developed as a result of exposure to sunlight), Oral or nasopharyngeal ulcers,
Hematologic disorders (hemolytic anemia, leukopenia, lymphopenia, or
thrombocytopenia), Immunologic disorders (antibodies against double-stranded DNA
[dsDNA] or Smith [Sm] antigen, false-positive serologic test for syphilis, or
antiphospholipid antibodies [anticardiolipin antibody or lupus anticoagulant]),
, lOMoAR cPSD| 67691079
Nonerosive arthritis of at least two peripheral joints, Serositis (pleurisy, pericarditis),
Renal disorder (persistent proteinuria of >0.5 g/day or >3 g/day on dipstick or cellular
casts), Neurologic disorders (seizures or psychosis in the absence of known causes),
Presence of antinuclear antibody (ANA)
Autoimmunity Familial Autoimmune Diseases
• Affected family members may not all develop the same disease, but several members
may have different disorders characterized by a variety of hypersensitivity reactions
• Associations with autoimmune diseases have been identified for a variety of major
histocompatibility complex (MHC) alleles or non-MHC genes Alloimmunity
• Immune system reacts against antigens on the tissues of other members of the same
species
• Examples: Neonatal disease where the maternal immune system becomes sensitized
against antigens expressed by the fetus, Transplant rejection, Transfusion reaction
Hypersensitivity: Type 4
Delayed Response
Does not involve antigen/antibody complexes like Types I, II and III
Is T-cell mediated
Relationship between Type II and Type IV Hypersensitivity Reactions
• Organ rejection involves cytotoxicity (Type II)
• T-cells play a major role in organ rejection (Type IV-completely T-cell mediated)
• Antigens from target cells stimulate T-cells to differentiate into cytotoxic (Type II) T-cells
• These T-cells have direct cytotoxic activity along with help T-cells involved in delayed
hypersensitivity (type IV)
Differentiating Between the Rash of a Type 1 vs. Type IV Reaction
• Type I: Immediate, atopic, generalized lesions
• Type IV: delayed, contact, lesions on at site of contact (poison ivy) Treatment of Type
IV Rash
• non-severe: topical corticosteroid
• Why wouldn’t we use epinephrine or antihistamines? Epinephrine is for emergent Type 1
anaphylactic reactions, Antihistamines act on the H1 receptors, Type IV doesn’t involve
mast cells and H1 receptors
Hypersensitivity Reactions and Hematologic Disorders Study Guide
Hypersensitivity: Type 1 Allergic Reaction Mediated by IgE
• Inflammation due to mast cell degranulation
• Local symptoms: itching, rash
• Systemic symptoms: wheezing
• Most dangerous form is an anaphylactic reaction-systemic response-hypotension,
severe bronchoconstriction, tx: epinephrine reverses the effects
Hypersensitivity: Type 2 Cytotoxic Reaction; Tissue Specific (thyroid)
• Macrophages are the primary effectors cells involved
• Can cause tissue damage or alter function
• Grave’s disease (hyperthyroidism)-example of altering thyroid function, but does not
destroy thyroid tissue
• Incompatible blood type: example of cell/tissue damage that occurs; severe transfusion
reaction occurs, transfused erythrocytes are destroyed by agglutination or
complementmediated lysis
Difference Between Type 2 and Type 3
• Type 2 is organ specific; the antibody binds to the antigen on the cell surface
• Type 3 is not organ specific; the antibody binds to soluble antigen outside the cell
surface that was released into the blood or body fluids, and the complex is then
deposited in the tissues
Hypersensitivity: Type 3
Examples
• Rheumatoid Arthritis: Antigen/antibodies are deposited in the joints
• Systemic Lupus Erythematosus (SLE): Antigen/antibodies deposit in organs that cause
tissue damage
• Scope of Damage of SLE-Type 3-autoimmune response (Lupus): Facial rash confined to
the cheeks (malar rash), Discoid rash (raised patches, scaling), Photosensitivity (skin
rash developed as a result of exposure to sunlight), Oral or nasopharyngeal ulcers,
Hematologic disorders (hemolytic anemia, leukopenia, lymphopenia, or
thrombocytopenia), Immunologic disorders (antibodies against double-stranded DNA
[dsDNA] or Smith [Sm] antigen, false-positive serologic test for syphilis, or
antiphospholipid antibodies [anticardiolipin antibody or lupus anticoagulant]),
, lOMoAR cPSD| 67691079
Nonerosive arthritis of at least two peripheral joints, Serositis (pleurisy, pericarditis),
Renal disorder (persistent proteinuria of >0.5 g/day or >3 g/day on dipstick or cellular
casts), Neurologic disorders (seizures or psychosis in the absence of known causes),
Presence of antinuclear antibody (ANA)
Autoimmunity Familial Autoimmune Diseases
• Affected family members may not all develop the same disease, but several members
may have different disorders characterized by a variety of hypersensitivity reactions
• Associations with autoimmune diseases have been identified for a variety of major
histocompatibility complex (MHC) alleles or non-MHC genes Alloimmunity
• Immune system reacts against antigens on the tissues of other members of the same
species
• Examples: Neonatal disease where the maternal immune system becomes sensitized
against antigens expressed by the fetus, Transplant rejection, Transfusion reaction
Hypersensitivity: Type 4
Delayed Response
Does not involve antigen/antibody complexes like Types I, II and III
Is T-cell mediated
Relationship between Type II and Type IV Hypersensitivity Reactions
• Organ rejection involves cytotoxicity (Type II)
• T-cells play a major role in organ rejection (Type IV-completely T-cell mediated)
• Antigens from target cells stimulate T-cells to differentiate into cytotoxic (Type II) T-cells
• These T-cells have direct cytotoxic activity along with help T-cells involved in delayed
hypersensitivity (type IV)
Differentiating Between the Rash of a Type 1 vs. Type IV Reaction
• Type I: Immediate, atopic, generalized lesions
• Type IV: delayed, contact, lesions on at site of contact (poison ivy) Treatment of Type
IV Rash
• non-severe: topical corticosteroid
• Why wouldn’t we use epinephrine or antihistamines? Epinephrine is for emergent Type 1
anaphylactic reactions, Antihistamines act on the H1 receptors, Type IV doesn’t involve
mast cells and H1 receptors
