Immunology: Recognition, Effector Function, and Tolerance
Immune Recognition
Innate and adaptive layers
The immune system distinguishes self from non-self, but modern immunology emphasizes damage, context, and learned tolerance rather than a simplistic binary. Innate immunity uses pattern-recognition receptors, complement, phagocytes, and interferons to detect conserved microbial or danger-associated signals. Adaptive immunity generates diverse antigen receptors through somatic recombination, enabling specificity, memory, and clonal expansion.
What is the main consequence of V(D)J recombination?
V(D)J recombination produces diverse antigen receptor repertoires needed for adaptive immunity.
Correct answer: Generation of receptor diversity in B and T cells
What is immunological tolerance?
Tolerance is essential to avoid autoimmunity and excessive inflammation.
Correct answer: A state in which immune responses to self or harmless antigens are actively prevented or restrained.
Effector Mechanisms and Pathology
Antibodies, T cells, and cytokine networks
B cells generate antibodies that neutralize pathogens, opsonize targets, and activate complement. T cells coordinate immunity via helper functions, cytotoxic killing, and regulatory suppression. Cytokine networks integrate innate and adaptive responses, but dysregulation can produce autoimmunity, immunodeficiency, allergy, cytokine storm, or chronic inflammation.
Which cell type is most directly responsible for antigen-specific cytotoxic killing of infected host cells?
CD8 cytotoxic T cells recognize antigenic peptides on MHC class I and induce target cell death.
Correct answer: Cytotoxic T lymphocytes
Why can excessive cytokine signaling be harmful?
Immune responses must be tightly regulated to prevent collateral injury.
Correct answer: Because it can cause systemic inflammation, tissue damage, vascular leakage, and organ dysfunction.