Immune System Flashcards

Pathogens

  • Pathogens are disease-causing agents that disrupt normal physiology.

  • They can be cellular (bacteria, fungi, parasites) or non-cellular (viruses, prions).

  • Viruses insert genetic material into host cells to multiply.

  • Prions are infectious proteins with abnormal folding.

  • Bacteria reproduce quickly and compete with host cells.

  • Fungi colonize body surfaces.

  • Parasites feed on a host (microparasites/protozoa or macroparasites/helminths).

Immune System - Lines of Defense

  • First line: Surface barriers prevent pathogen entry.

  • Second line: Non-specific defenses activated after infection.

  • Third line: Specific responses target antigens from pathogens.

Surface Barriers

  • Physical barriers: obstruct access (e.g., skin, mucous membranes).

  • Chemical barriers: hinder survival via chemical compounds (e.g., gastric secretions, sweat).

  • Microbiological barriers: Natural flora prevent colonization.

Clotting

  • Restores intact external layer when surface barriers are penetrated.

  • Initiated by clotting factors from damaged cells/platelets.

  • Prothrombin converts to thrombin, fibrinogen to fibrin, forming a clot.

Innate Immune System

  • Non-specific defense; responds the same way every time.

  • Phagocytic leukocytes internalize and digest pathogens.

  • Phagocytes recruited by chemotactic chemicals.

  • Lymphatic system filters fluid (lymph) and removes pathogens.

  • Antigen-presenting cells (APCs) transport antigens to lymphocytes.

Adaptive Immune System

  • Specific defense; recognizes specific antigens.

  • Produces heightened response upon re-exposure (immunological memory).

  • Lymphocytes in lymph nodes are principal components.

Antigens

  • Molecular markers on pathogen surfaces.

  • Targeted by antibodies.

Lymphocytes

  • B and T lymphocytes recognize specific antigens.

  • Clonal selection/expansion: lymphocyte activated to divide & form clones.

  • Helper T cells coordinate adaptive response, activate B lymphocytes.

  • B cells form plasma cells (produce antibodies) and memory cells.

Antibodies

  • Proteins produced by B lymphocytes specific to an antigen.

  • Y-shaped molecules with variable regions for antigen specificity.

  • Facilitate pathogen destruction via opsonization, etc.

Memory Cells

  • Produced when B and T lymphocytes divide.

  • Enable faster, more potent secondary immune response.

  • Provide immunological memory and immunity.

Immunodeficiency

  • Compromised or absent immune system.

  • HIV infects helper T lymphocytes, leading to AIDS.

  • Transmitted via bodily fluids.

Antibiotics

  • Target prokaryotic features in bacteria.

  • Antibiotic resistance develops via mutations and gene transfer.

Vaccination

  • Injection of attenuated pathogens/antigenic fragments to provide active acquired immunity.

  • Initiates primary response and memory cell production.

  • Secondary response prevents disease symptoms upon exposure.

Herd Immunity

  • Indirectly protects non-vaccinated individuals when a large percentage of population is immune.

  • Limits pathogen spread.

Outbreaks

  • Epidemic: outbreak in a community/region.

  • Pandemic: outbreak across a wider geographical area.