Immunology: Antibodies and Functions

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What is the primary function of the secretory component (SC) in the context of IgA antibodies?

To transport IgA across the placenta
To mediate binding of antibodies to mucin in the mucus layer (correct)
To enhance opsonization of pathogens by IgA
To facilitate binding of IgA to Fc receptors

Which of the following accurately describes how maternal IgG is transferred to a fetus?

It enters circulation through lymphatic vessels
It is actively secreted through breast milk
It is synthesized by the fetus during pregnancy
It is transported across the placenta by the neonatal Fc receptor (FcRn) (correct)

How do antibodies contribute to neutralization of toxins?

By promoting phagocytosis via opsonization
By binding to receptor-binding sites of toxins to prevent cell entry (correct)
By enhancing the immune response through complement activation
By inducing apoptosis in infected cells

What role does FcRn play in adults?

It maintains plasma levels of IgG and prevents its excretion (C) Signup and view all the answers

What is the mechanism of antibody-mediated opsonization?

Antibodies bind to extracellular pathogens marking them for phagocytosis (C) Signup and view all the answers

Which type of antibody is predominantly secreted in breast milk to protect newborns?

IgA (D) Signup and view all the answers

In what form does IgA predominantly exist when secreted from plasma cells?

Dimeric form (A) Signup and view all the answers

What happens to IgG antibodies that are ingested from maternal milk?

They are absorbed and transported into the bloodstream by FcRn (C) Signup and view all the answers

What is the primary function of virus-neutralizing antibodies?

To block binding of viruses to surface receptors (A) Signup and view all the answers

How do high-affinity IgG and IgA antibodies contribute to neutralization of toxins?

By neutralizing toxins and blocking infectivity (D) Signup and view all the answers

What is the role of Fc receptors on phagocytes?

They enhance the recognition and ingestion of pathogens (A) Signup and view all the answers

What consequences can arise from the failure to remove immune complexes from circulation?

They can cause tissue damage in small blood vessels (B) Signup and view all the answers

Which type of receptor is most closely associated with triggering exocytosis in mast cells during allergic reactions?

FcεRI (C) Signup and view all the answers

What mechanism primarily allows natural killer (NK) cells to kill antibody-coated target cells?

Antibody-dependent cell-mediated cytotoxicity (ADCC) (B) Signup and view all the answers

Which immunoglobulin is primarily involved in the allergic response by binding to mast cells?

IgE (B) Signup and view all the answers

What is the primary role of IgA antibodies in mucosal surfaces?

Inhibit colonization by pathogens (A) Signup and view all the answers

What type of antigens does the FcγR receptor family specifically recognize?

IgG antibodies (C) Signup and view all the answers

Which type of complement activation pathway is triggered by antibody:antigen complexes?

Classical pathway (C) Signup and view all the answers

IgA transport

IgA antibodies are transported across mucosal epithelial surfaces, primarily from the lamina propria to the lumen of the gut.

Secretory Component

A part of the polymeric immunoglobulin receptor (pIgR) that is cleaved off and helps IgA bind to mucus and prevent enzymes or Fc receptors from affecting the antibody.

Maternal IgG transport

IgG antibodies from the mother are transported across the placenta to the fetus via the neonatal Fc receptor (FcRn).