Immunology & Serology Flashcards

Which immunoglobulin is primarily involved in allergic reactions?

Answer: IgE

Immunoglobulin E (IgE) is the primary antibody class responsible for mediating allergic reactions and responses to parasitic infections. When an allergen is encountered, IgE binds to mast cells and basophils, triggering the release of histamine and other inflammatory mediators. This cascade of events leads to the characteristic symptoms of allergies, such as hives, sneezing, or anaphylaxis.

What is the first antibody produced in a primary immune response?

Answer: IgM

Immunoglobulin M (IgM) is the first antibody produced and secreted by plasma cells during a primary immune response to a new antigen. Its pentameric structure allows it to efficiently bind multiple antigens, making it highly effective at activating the complement system and agglutinating pathogens. While other antibodies like IgG appear later, IgM provides immediate, short-term protection.

Which test is commonly used to detect antibodies to HIV?

Answer: ELISA

ELISA (Enzyme-Linked Immunosorbent Assay) is a widely used and highly sensitive screening test for detecting antibodies to HIV in a blood sample. It works by using an enzyme-linked antibody to detect the presence of specific antibodies or antigens, indicating exposure to the virus. While Western blot is a confirmatory test and PCR detects viral genetic material, ELISA is the standard initial screening method due to its cost-effectiveness and high throughput.

What is the primary function of T-helper cells?

Answer: Activate B cells and immune cells

T-helper cells (CD4+ T cells) are crucial orchestrators of the adaptive immune response. They recognize antigens presented by antigen-presenting cells and then release cytokines that activate other immune cells, including B cells to produce antibodies, cytotoxic T cells to kill infected cells, and macrophages. This activation is essential for coordinating an effective and targeted immune response against pathogens.

Which complement pathway is activated by antigen-antibody complexes?

Answer: Classical

The classical complement pathway is primarily activated by the binding of antibodies (specifically IgG or IgM) to antigens, forming antigen-antibody complexes. This binding initiates a cascade of protein interactions, leading to the formation of the membrane attack complex (MAC) and subsequent lysis of target cells. The alternative and lectin pathways are activated by different triggers.

Which serological test is used to detect syphilis?

Answer: RPR

RPR (Rapid Plasma Reagin) is a non-treponemal serological test commonly used to screen for syphilis. It detects antibodies (reagins) produced by the body in response to tissue damage caused by the syphilis bacterium, Treponema pallidum. While other tests exist, RPR is a widely adopted and cost-effective screening method, often followed by a treponemal test for confirmation.

What is the role of memory B cells?

Answer: Provide long-term immunity

Memory B cells are a subset of B lymphocytes that 'remember' specific antigens encountered during a previous infection or vaccination. Upon re-exposure to the same antigen, these cells rapidly differentiate into plasma cells and produce large quantities of antibodies. This rapid and robust secondary immune response is the basis of long-term immunity, protecting the individual from future infections by the same pathogen.

Which immunoglobulin can cross the placenta?

Answer: IgG

Immunoglobulin G (IgG) is the only antibody class capable of crossing the placenta from mother to fetus. This crucial ability provides passive immunity to the newborn, protecting them from various infections during the first few months of life before their own immune system is fully developed. IgG is also the most abundant antibody in serum and plays a major role in secondary immune responses.

Which autoimmune disorder is associated with anti-nuclear antibodies (ANA)?

Answer: Systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that target various components of the body's own cells, including the cell nucleus. Anti-nuclear antibodies (ANA) are a hallmark of SLE, present in nearly all patients, and are a key diagnostic marker for the condition. While other autoimmune diseases may have ANAs, SLE is most strongly associated with them.