Human Immune System & Vaccines GK Questions & Answers
The human immune system defends the body against pathogenic microorganisms through coordinated innate and adaptive mechanisms. Innate immunity provides non-specific, immediate defense through anatomical barriers such as the stratum corneum of skin, physiological secretions including hydrochloric acid (pH 1.5 to 3.5) in the stomach, lysozyme in saliva, and phagocytic leukocytes comprising neutrophils, monocytes, and natural killer (NK) cells. Adaptive immunity offers antigen-specific defense characterized by immunological memory, mediated by B-lymphocytes and T-lymphocytes originating in primary lymphoid organs—the bone marrow and thymus. B-cells differentiate into plasma cells to synthesize five classes of immunoglobulins: IgG (most abundant, crosses the placental barrier), IgA (secretory antibody in colostrum and mucosal linings), IgM (pentameric, primary immune responder), IgD, and IgE (mediates type-I hypersensitivity and parasitic responses). Cell-mediated immunity involves CD4+ helper T-cells and CD8+ cytotoxic T-cells, which recognize peptides presented by Major Histocompatibility Complex (MHC Class I and II) molecules encoded on human chromosome 6. Vaccinology originated with Edward Jenner in 1796 using cowpox inoculation against smallpox, followed by Louis Pasteur developing attenuated rabies and anthrax vaccines. Active immunization stimulates host memory cells, whereas passive immunization delivers preformed antibodies for immediate protection.
High-yield conceptual summaries for competitive exams and rapid revision.
Innate immunity represents the non-specific, first line of defense present from birth, including physical, chemical, and cellular barriers.
Primary lymphoid organs comprise the bone marrow and thymus, where immature lymphocytes originate, proliferate, and undergo maturation.
Secondary lymphoid organs include the spleen, lymph nodes, tonsils, and Peyer's patches, where mature lymphocytes encounter antigens and initiate immune responses.
B-lymphocytes mature in the bone marrow and mediate humoral immunity by differentiating into antibody-secreting plasma cells and memory cells.
T-lymphocytes mature in the thymus and mediate cell-mediated immunity, differentiating into CD4+ helper T-cells and CD8+ cytotoxic T-cells.
Antibodies are Y-shaped glycoproteins termed immunoglobulins composed of two identical heavy chains and two identical light chains joined by disulfide bonds.
Immunoglobulin G (IgG) constitutes approximately 75 to 80 percent of total serum antibodies and is the only immunoglobulin capable of crossing the human placenta.
Secretory Immunoglobulin A (IgA) occurs as a dimer in body fluids such as colostrum, saliva, tears, and gastrointestinal mucus, providing localized mucosal defense.
Immunoglobulin M (IgM) exists as a pentameric structure with ten antigen-binding sites and serves as the earliest antibody synthesized during primary immune response.
Immunoglobulin E (IgE) binds to high-affinity receptors on mast cells and basophils, triggering histamine release during allergic reactions and parasitic infections.
Major Histocompatibility Complex (MHC) genes on human chromosome 6 encode surface proteins that display peptide antigens to circulating T-cells.
Edward Jenner pioneered vaccination in 1796 by utilizing cowpox material to induce cross-protective immunity against the deadly smallpox virus.
Louis Pasteur developed the germ theory of disease and formulated the earliest laboratory-developed attenuated vaccines for chicken cholera, anthrax, and rabies.
Active immunity results from direct antigen exposure stimulating endogenous memory cell generation, while passive immunity confers transient protection via preformed antibodies.
Autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and type-1 diabetes arise when self-tolerance fails and the immune system attacks host tissues.
Administering preformed human or equine antibodies (such as rabies immune globulin or antivenom) to provide immediate, transient therapeutic neutralization of pathogens or toxins confers which type of immunity?
Verified Explanation
Passive artificial immunity involves the direct parenteral administration of preformed exogenous antibodies (such as intravenous immunoglobulins, hyperimmune globulins, or snake antivenom). It provides immediate, temporary post-exposure protection because it does not require an active host adaptive immune response; however, it confers no immunological memory, and protective antibody levels decay within weeks to months.
2ID: GK-BODY-00844
easyVaccines, Immunology & Public Health
Which immunoglobulin isotype is the only class of antibody capable of selectively crossing the human placenta from maternal blood into fetal circulation to confer passive neonatal immunity?
Verified Explanation
Immunoglobulin G (IgG) is the sole antibody class that actively traverses the syncytiotrophoblast of the human placenta. This transport is mediated by the neonatal Fc receptor (FcRn), which binds the Fc region of maternal IgG in acidic endosomes and transcytoses it into fetal circulation, providing the newborn infant with protective humoral immunity that persists for several months after birth.
3ID: GK-OCEN-00250
hardUNCLOS, EEZ & Blue Economy Policy
Under Article 236 of UNCLOS, what specific legal exemption is granted regarding 'Sovereign Immunity' from environmental enforcement provisions for warships and state-owned naval vessels?
Verified Explanation
UNCLOS Article 236 explicitly preserves sovereign immunity, stipulating that the environmental protection provisions of the Convention do not apply to warships, naval auxiliaries, or other vessels/aircraft owned or operated by a State on government non-commercial service, while obligating flag states to adopt appropriate non-prejudicial measures.
4ID: GK-WPOL-00480
easyDiplomatic Relations
Which 1961 international treaty codifies the modern rules and privileges of diplomatic immunity and relations between sovereign states?
Verified Explanation
The Vienna Convention on Diplomatic Relations (1961) is an international treaty that defines the framework for diplomatic relations between independent countries, including embassy inviolability and diplomatic immunity.
5ID: GK-WPOL-00534
easyDiplomatic Relations
Which fundamental multilateral treaty signed in 1961 codified the modern framework of diplomatic relations and diplomatic immunity?
Verified Explanation
Adopted in 1961 and in force since 1964, the Vienna Convention on Diplomatic Relations governs diplomatic missions, inviolability of embassy premises, and diplomatic immunity.
6ID: GK-BIZ-00119
hardStartup Ecosystem, Unicorns & IBC Insolvency
Under Section 32A of the IBC (inserted in 2020), under what condition is a corporate debtor granted complete statutory immunity from liability and prosecution for offences committed prior to the commencement of CIRP?
Verified Explanation
Section 32A of the IBC provides that the liability of a corporate debtor for an offence committed prior to the commencement of the CIRP shall cease, and the corporate debtor shall not be prosecuted, from the date the resolution plan is approved by the NCLT, provided the resolution plan results in a change in management to persons unconnected with the erstwhile promoters.
7ID: GK-BODY-00492
mediumVaccines Immunology
Which class of immunoglobulins is the only antibody capable of crossing the human maternal placenta to confer passive congenital immunity to the fetus?
Verified Explanation
Immunoglobulin G (IgG) is the predominant serum antibody isotype and the only immunoglobulin capable of actively crossing the placenta via neonatal Fc receptors (FcRn).
8ID: GK-BODY-00854
easyVaccines, Immunology & Public Health
Which class of human immunoglobulin is uniquely capable of crossing the placental barrier to confer passive maternal immunity to the developing fetus?
Verified Explanation
Immunoglobulin G (IgG) is the only human antibody class that can actively cross the placenta from maternal circulation into fetal blood. This transport is mediated by the neonatal Fc receptor (FcRn) expressed on syncytiotrophoblast cells of the placenta. Maternal IgG provides vital passive humoral protection to the fetus and newborn infant against common pathogens during the first four to six months of life while the neonatal immune system matures.
9ID: GK-BODY-00872
easyVaccines, Immunology & Public Health
Which category of vaccines contains living microorganisms that have been weakened in virulence so they replicate sufficiently to stimulate immunity without causing clinical disease?
Verified Explanation
Live attenuated vaccines contain viable pathogens that have been repeatedly passaged in non-human host cells or genetically modified to diminish virulence while retaining immunogenicity. When injected, the attenuated organism replicates inside host cells, stimulating strong, enduring humoral and cell-mediated (cytotoxic T cell) immune responses that closely mirror natural infection. Well-known examples include the measles, mumps, and rubella (MMR), oral polio (Sabin), and yellow fever vaccines.
10ID: GK-POL-00647
hardFundamental Rights, DPSP & Fundamental Duties
Article 31C of the Constitution, as upheld in Kesavananda Bharati, gives legal immunity to laws enacted to give effect to the socialist Directive Principles in which clauses of Article 39?
Verified Explanation
Article 31C (inserted by the 25th Amendment Act 1971) shields laws implementing Article 39(b) [distribution of material resources] and 39(c) [prevention of concentration of wealth] from challenge under Articles 14 and 19.
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