Free Immunology MCQs with Answers

• A. Suquestrated antigens
• B. Isoantigens
• C. Haptens
• D. Heterophile antigens

Explanation: Heterophile antigens are identical or closely related antigens found in unrelated biological species.

• A. Type I
• B. Type II
• C. Type III
• D. Type IV

Explanation: Rh incompatibility is a Type II hypersensitivity because maternal IgG antibodies bind fetal Rh-positive red-cell antigens and promote…

• A. Type I
• B. Type II
• C. Type III
• D. Type IV

Explanation: Killer-cell activity in this classification refers mainly to antibody-dependent cellular cytotoxicity, in which NK cells destroy…

• A. Arthus reaction
• B. SLE
• C. Auto immune hemolytic anemia
• D. Contact dermatitis

Explanation: Autoimmune haemolytic anaemia is a classic Type II reaction because antibodies bind red-cell surface antigens and cause cell destruction.

• A. Xenograft
• B. Autograft
• C. Allograft
• D. Isograft

Explanation: A graft between genetically identical individuals, such as identical twins, is an isograft.

• A. IgA
• B. IgG
• C. IgM
• D. IgE

Explanation: Type I hypersensitivity is driven by allergen-specific IgE, which binds mast cells and basophils and triggers mediator release on…

• A. Bacterial products
• B. Toxoids
• C. Vaccines
• D. Antitoxins

Explanation: Antitoxins contain preformed antibodies, so they provide passive artificial immunity rather than stimulating the recipient to make its own…

• A. IgM antibodies
• B. Lysozyme
• C. Mast cells
• D. IgA antibodies

Explanation: Secretory IgA in breast milk survives mucosal conditions and prevents microbes from attaching to the infant’s intestinal and respiratory…

• A. Plasma cells
• B. Activated macrophages
• C. Lymphocytes
• D. Platelet

Explanation: Activated macrophages release IL-1 and TNF-α, which promote fever, endothelial activation and other features of acute inflammation.

• A. Disproportionate antigen antibody levels
• B. Excess antigen
• C. Excess antibody
• D. Hyper immune reaction

Explanation: The prozone is the antibody-excess zone of an antigen-antibody reaction, where very large amounts of antibody prevent optimal lattice…

• A. Radioimmuno Assay
• B. ELISA
• C. Immunoflourescence
• D. Passive hemaglutination

Explanation: Radioimmunoassay can detect very small quantities of antigen because the radioactive signal is highly sensitive.

• A. IgG & igM
• B. IgG & IgA
• C. IgG & IgD
• D. IgD & IgE

Explanation: The classical complement pathway is activated when antigen-bound IgM or IgG exposes Fc regions that bind C1.

• A. Acts as a mucosal barrier for infection
• B. Circulating antibody
• C. Kills virus infected cells
• D. Activates macrophages

Explanation: IgA, especially secretory IgA, forms a mucosal barrier by neutralising microbes and blocking their attachment to epithelial surfaces.

• A. Idiotope
• B. Paratope
• C. Epitope
• D. Hapten

Explanation: The paratope is the antigen-binding site on an antibody, formed mainly by its variable regions.

• A. Forssman antigen antibody reaction
• B. Weil-Felix reaction
• C. Paul bunnel reaction
• D. Widal reaction

Explanation: Forssman, Weil-Felix, and Paul-Bunnell reactions depend on heterophile antibodies reacting with antigens found in unrelated species.

• A. Increase toxigenicity
• B. Increase antigenicity
• C. Reduce the antigenicity
• D. reduce the toxigenicity

Explanation: An adjuvant enhances the immune response to an antigen, effectively increasing its immunogenicity or antigenicity.

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: IgG has four subclasses: IgG1, IgG2, IgG3, and IgG4. They differ in properties such as complement activation and placental transfer.

• A. antigenic and toxic
• B. antigenic and non-toxic
• C. non-antigenic and toxic
• D. non-antigenic and non-toxic

Explanation: A toxoid is a toxin chemically or physically inactivated so that it loses toxicity but retains antigenicity.

• A. Functional differences
• B. Structural differences
• C. Complemented fixation
• D. None of the above

Explanation: Human immunoglobulin classes are distinguished primarily by structural differences in their heavy chains, which also produce functional…

• A. 1 hour
• B. 1 day
• C. 1 week
• D. 1 Month

Explanation: IgG has an average half-life of about 21 to 23 days, which is approximately one month among the given choices.