SEROIM MIDTERM - COMPREHENSIVE

Lysozyme

Enzyme that hydrolyzes β-(1,4)-glycosidic bonds between NAM and NAG in bacterial peptidoglycan.

TLR4

Transmembrane PRR that detects extracellular bacterial lipopolysaccharide (LPS).

TLR5

Transmembrane PRR that detects bacterial flagellin.

TLR9

Endosomal PRR that detects internalized unmethylated CpG DNA.

Inflammasome

Multiprotein cytosolic complex consisting of NLRP3, ASC, and pro-caspase-1 that senses danger signals.

Caspase-1

Inflammasome-activated protease that cleaves pro-IL-1β and pro-IL-18 into active cytokines.

C-Reactive Protein (CRP)

Pentameric positive acute-phase reactant that acts as an opsonin and fixes C1q.

Beta-2 Microglobulin (β2M)

Non-polymorphic light chain required for MHC Class I stability and surface expression.

TAP1/TAP2

ATP-dependent ER membrane transporters that shuttle cytosolic peptides into the ER for MHC Class I presentation.

Invariant Chain (CD74)

ER chaperone that blocks premature endogenous peptide binding to MHC Class II.

HLA-DM

Endosomal chaperone that removes CLIP to allow exogenous peptides to bind MHC Class II.

Bare Lymphocyte Syndrome Type I (BLS-I)

Immunodeficiency caused by TAP1, TAP2, or tapasin defects, resulting in absent surface MHC Class I and reduced CD8+ T cells.

Bare Lymphocyte Syndrome Type II (BLS-II)

Immunodeficiency caused by CIITA/RFX mutations, resulting in absent surface MHC Class II and profound CD4+ T-cell deficiency.

Leukocyte Adhesion Deficiency Type 1 (LAD-1)

ITGB2 (CD18) defect causing impaired leukocyte adhesion, delayed umbilical cord detachment, neutrophilic leukocytosis, and infections with little or no pus.

NADPH Oxidase

Phagocyte enzyme complex that generates superoxide by transferring electrons from NADPH to oxygen.

Myeloperoxidase (MPO)

Neutrophil azurophilic granule enzyme that uses H₂O₂ and chloride to produce hypochlorous acid (HOCl).

Chronic Granulomatous Disease (CGD)

NADPH oxidase deficiency causing defective superoxide production, susceptibility to catalase-positive organisms, and a negative NBT test.

DHR-123 Flow Cytometry

Test measuring PMA-induced NADPH oxidase activity through oxidation to fluorescent rhodamine 123.

NK Cell Surface Markers

CD16+, CD56+, CD3−.

Missing-Self Hypothesis

Principle that NK cells kill target cells with absent or downregulated self-MHC Class I.

C3bBb

Alternative complement pathway C3 convertase stabilized by properdin.

Membrane Attack Complex (MAC / C5b-9)

Complement pore formed by polymerized C9 that causes target-cell lysis.

Paroxysmal Nocturnal Hemoglobinuria (PNH)

PIGA mutation causing loss of GPI-anchored CD55 and CD59, leading to uncontrolled complement-mediated intravascular hemolysis.

CD28

Constitutive T-cell receptor that binds APC B7-1 (CD80) and B7-2 (CD86) to provide costimulatory Signal 2.

CTLA-4 (CD152)

Inhibitory checkpoint receptor that binds B7 with higher affinity than CD28 and promotes peripheral tolerance.

Perforin

Calcium-dependent CTL granule protein that forms pores in target-cell membranes.

Fas/FasL Pathway

Calcium-independent CTL apoptosis pathway involving CD95L binding CD95, DISC formation, and caspase-8 activation.

Familial Hemophagocytic Lymphohistiocytosis (FHL)

Genetic cytolytic granule defect causing uncontrolled cytokine release and hemophagocytosis.

Autoimmune Lymphoproliferative Syndrome (ALPS)

Fas/FasL apoptosis defect causing defective AICD, lymphadenopathy, splenomegaly, and double-negative T cells.

Acridinium Ester

Chemiluminescent marker producing a rapid flash emission when triggered by alkaline H₂O₂.

High-Dose Hook Effect

Extreme antigen excess in a one-step sandwich assay causing falsely low results.

Heterophile Antibodies / HAMA

Non-human patient antibodies that cross-link animal antibodies in sandwich immunoassays, causing false-positive results.

Rheumatoid Factor (RF)

Endogenous IgM anti-IgG Fc that can cause false bridging in immunoassays.

CD79a/CD79b (Ig-α/Ig-β)

Disulfide-linked signaling heterodimer associated with mIgM/mIgD and containing cytoplasmic ITAMs.

Bruton Tyrosine Kinase (BTK)

Cytosolic tyrosine kinase downstream of the pre-BCR; mutations cause X-linked agammaglobulinemia.

CD19/CD21/CD81

B-cell coreceptor complex that amplifies BCR activation signaling.

Dark Zone

Germinal center region rich in CXCL12 where centroblasts proliferate rapidly and undergo AID-driven somatic hypermutation.

Activation-Induced Cytidine Deaminase (AID)

B-cell nuclear enzyme that converts cytidine to uracil to initiate somatic hypermutation and class-switch recombination.

CD40-CD40L (CD154) Axis

Essential B-cell-Tfh costimulatory pathway required for class switching and germinal center reactions.

Protein-Polysaccharide Conjugate Vaccine

Vaccine linking capsular polysaccharides to a protein carrier to recruit T-cell help in children under 2 years.

Four-Fold Titer Rise Rule

Diagnostic criterion requiring a fourfold antibody titer increase between paired acute and convalescent sera collected 10-14 days apart.

C4b2a

Classical complement pathway C3 convertase.

C4b2a3b

Classical complement pathway C5 convertase.

Immune Adherence

Removal of immune complexes when RBC CR1 (CD35) binds C3b/C4b-coated complexes for hepatic or splenic clearance.

Hereditary Angioedema (HAE)

Autosomal dominant C1 inhibitor deficiency associated with low C4, normal C3, and excessive kallikrein/bradykinin generation.