Parasitology: Host Defense and Parasite Evasion

Comprehensive vocabulary flashcards focusing on host defense systems, comparative immunology, and parasite immune evasion strategies from Chapter 4 of Parasitology: A Conceptual Approach.

Restriction-Modification System

An early bacterial immune defense mechanism capable of self-nonself recognition, wherein restriction endonucleases (REase) cleave foreign, unmethylated DNA (such as bacteriophage DNA) while host methyltransferases (MTase) protect host DNA via methylation.

CRISPR-Cas System

A bacterial adaptive immune system providing acquired-like immunity and exemplifying Lamarckian inheritance; bacteria capture and incorporate snippets of invading viral DNA as spacers into repetitive arrays, transcribing them into crRNA that guides Cas endonuclease complexes to cleave homologous viral nucleic acids upon reinfection.

Pattern-Triggered Immunity (PTI)

A plant cell-surface defense mechanism activated when transmembrane pattern recognition receptors (PRRs) detect and bind pathogen-associated molecular patterns (PAMPs).

Effector-Triggered Immunity (ETI)

An intracellular plant immune response where intracellular nucleotide-binding leucine-rich repeat proteins (NB-LRRs) encoded by resistance (R) genes recognize specific parasite effector proteins injected to degrade host signaling.

Stylet

A sharp, hollow, retractable mouth spear possessed by plant-parasitic nematodes, used to mechanically tease apart adjacent host plant cells and inject gland secretions.

Caenopores

Pore-forming antimicrobial peptides produced by the nematode Caenorhabditis elegans to defend against microbial pathogens in the absence of circulating hemocytes.

Fibrinogen-Related Proteins (FREPs)

Lectin-like defense molecules produced by gastropod snails (such as Biomphalaria) that mediate non-self recognition and opsonization of invading trematodes like Schistosoma mansoni.

Innate Immune Memory (Invertebrate Immune Priming)

The heightened, enhanced secondary defense response observed in invertebrates (such as woodlice and Anopheles gambiae) upon re-exposure to pathogens, mediated by activated hemocytes or humoral factors despite lacking T and B lymphocytes.

Polydnavirus-Mediated Immunosuppression

A mutualistic strategy where endoparasitoid wasps inject virions replicating in calyx cells alongside eggs into host caterpillars; virally encoded proteins then discharge into caterpillar cells and suppress host cellular encapsulation.

Wigglesworthia glossinidia

An obligate intracellular bacterial symbiont housed in the bacteriome organ and milk gland of tsetse flies (Glossina morsitans) that provides essential vitamins, promotes immune and reproductive development, and protects against Escherichia coli infection.

Thioester-Containing Protein 1 (TEP-1)

An Anopheles mosquito hemolymph protein structurally analogous to vertebrate complement factor $C3$ that covalently binds to the surface of invading Plasmodium ookinetes to target them for lysis.

Premunition

A state of partial, non-sterilizing protective immunity to malaria in endemic areas maintained only by continuous, low-level exposure and repeated reinfection, preventing severe debilitating clinical manifestations.

Weep and Sweep Response

A Th2-driven intestinal helminth expulsion mechanism mediated by $IL-4$ and $IL-13$, characterized by increased goblet cell mucus secretion ('weep') and enhanced smooth muscle contractility and epithelial turnover ('sweep').

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

An effector immune mechanism against large parasites where specific IgE antibodies coat the helminth surface and bind to Fc receptors on eosinophils, mast cells, or basophils, triggering degranulation and release of cytotoxic products onto the cuticle.

Hemozoin-Mediated Oxidative Burst Inhibition

A parasite immune evasion mechanism wherein phagocytosed malarial biocrystal pigment (hemozoin) blocks protein kinase C (PKC) activation, preventing phosphorylation and assembly of the phagocyte NADPH oxidase complex and silencing $O_2^-$ production.

Variable Surface Glycoprotein (VSG)

A densely packed homodimeric surface coat protein of African trypanosomes (Trypanosoma brucei) possessing a conserved membrane-proximal C-terminus anchored by GPI and an antigenically variable N-terminal exposed domain.

VSG Pseudogene Transposition

The genomic mechanism underlying antigenic variation in Trypanosoma, where silent VSG pseudogenes from a reservoir of approximately $1000$ copies are sequentially copied and transposed into a single active telomeric expression site.

Interference with NF-κB Nuclear Translocation

An evasion strategy in which intracellular protozoa suppress host proinflammatory cytokine expression; Leishmania mexicana directly degrades the $I\text{-}\\\kappa B / NF\text{-}\\\kappa B$ complex, while Toxoplasma gondii blocks active $NF\text{-}\\\kappa B$ entry into the nucleus, preventing $IL-12$ transcription.

Inactivated C3b (iC3b)

A cleaved form of complement fragment $C3b$ generated on the promastigote surface of Leishmania by parasite surface proteases, preventing complement-mediated MAC assembly while promoting non-inflammatory uptake into host macrophages via complement receptors.

Schistosoma Complement Inhibitory Protein (SCIP)

A surface-associated evasion molecule produced by Schistosoma mansoni that binds to host complement factor $C9$, preventing terminal Membrane Attack Complex (MAC) polymerization and cell lysis.

Cystatins

Cysteine protease inhibitors secreted by parasitic filarial nematodes like Brugia malayi that inhibit host endosomal cathepsins, thereby impairing MHC class II antigen processing and presentation by dendritic cells.

Macrophage Migration Inhibitory Factor (MIF) Mimic

A cytokine mimic secreted by Brugia malayi that prevents classical proinflammatory activation of host macrophages and induces host FoxP3 expression, expanding immunosuppressive regulatory T (Treg) cells.