Interleukin-17 (IL-17) Test: Autoimmune Inflammation, Th17 Response, and Meaning
An interleukin-17 test measures a cytokine involved in barrier defense, neutrophil recruitment, and several immune-mediated inflammatory diseases. The name “IL-17” usually refers to IL-17A,...
Interleukin-18 (IL-18) Test: Inflammation, Macrophage Activation, and Hyperinflammation
An interleukin-18 test measures an inflammasome-related cytokine that can become markedly elevated in several hyperinflammatory disorders. Interleukin-18, abbreviated IL-18, is made as an inactive...
Interleukin-23 (IL-23) Test: Autoimmune Inflammation, Th17 Pathway, and Meaning
An interleukin-23 (IL-23) test measures a cytokine involved in type 17 immunity, a defense system that helps protect skin and mucosal surfaces from selected...
Lymphocyte Proliferation Test: T-Cell Function, Mitogen Response, and Immune Deficiency
A lymphocyte proliferation test evaluates whether living lymphocytes—especially T cells—can activate and divide after stimulation in the laboratory. It is a functional test, not...
Lymphocyte Subset Panel: T Cells, B Cells, NK Cells, CD4/CD8 Ratio, and Immune Function
A lymphocyte subset panel uses flow cytometry to count major immune-cell populations in blood, usually CD3 T cells, CD4 helper T cells, CD8 cytotoxic...
Macrophage Activation Syndrome Blood Test Panel: Ferritin, IL-18, Cytokines, and Hyperinflammation
A macrophage activation syndrome blood test panel is not one single laboratory test. It is a coordinated set of urgent studies used when clinicians...
Natural Killer Cell Count Test: NK Cells, Immune Function, and Viral Defense
A natural killer cell count test measures the number and percentage of circulating NK cells, usually by flow cytometry. Most laboratories identify NK cells...
Natural Killer Cell Function Test: NK Cell Activity, Immune Defense, and Meaning
A natural killer cell function test evaluates how well NK cells respond to stimulation or damage target cells in the laboratory. Depending on the...
Neutrophil Oxidative Burst Test: Chronic Granulomatous Disease Screening and Neutrophil Function
A neutrophil oxidative burst test measures whether neutrophils can generate reactive oxygen species after stimulation. The most widely used method is the dihydrorhodamine 123,...
Regulatory T-Cell Test: Tregs, Immune Tolerance, Autoimmunity, and Meaning
A regulatory T-cell test uses flow cytometry to estimate the number or percentage of circulating Tregs, most often within the CD4 T-cell population. Clinical...
Soluble IL-2 Receptor Test: Immune Activation, Inflammation, Sarcoidosis, and Lymphoma Risk
A soluble IL-2 receptor test measures circulating soluble interleukin-2 receptor alpha, also called sIL-2R alpha, sCD25, or soluble CD25. Activated lymphocytes and some other...
T-Cell Count Test: CD3 Cells, Immune Function, and Lymphocyte Subsets
A T-cell count test measures circulating lymphocytes that express CD3, the marker found on most mature T cells. Flow cytometry usually reports both the...
Transforming Growth Factor-Beta (TGF-Beta) Test: Immune Regulation, Fibrosis, and Meaning
A transforming growth factor-beta test measures a TGF-beta protein in blood, most often TGF-beta 1. TGF-beta regulates immune tolerance, wound repair, extracellular-matrix production, blood-vessel...
Tumor Necrosis Factor-Alpha (TNF-Alpha) Test: High Levels, Inflammation, and Cytokine Activity
A tumor necrosis factor-alpha test measures TNF-alpha, a powerful immune signaling protein involved in inflammation, infection defense, blood-vessel activation, fever, tissue repair, and cell...
Vascular Endothelial Growth Factor (VEGF) Test: Inflammation, Angiogenesis, and Blood Vessel Growth
A vascular endothelial growth factor test measures a protein signal involved in blood-vessel growth, vessel permeability, tissue repair, and responses to low oxygen. Most...
AH50 Complement Test: Alternative Pathway Activity, Low Levels, and Immune Function
The AH50 complement test measures whether the alternative complement pathway can complete its immune-defense cascade. This pathway is part of the innate immune system,...
C1 Esterase Inhibitor Antigen Test: Hereditary Angioedema, Low Levels, and Diagnosis
The C1 esterase inhibitor antigen test measures how much C1 inhibitor protein is present in the blood. It is a central test for hereditary...
C1 Esterase Inhibitor Function Test: Hereditary Angioedema, Functional Deficiency, and Diagnosis
The C1 esterase inhibitor function test checks whether C1 inhibitor protein can control the enzyme systems that generate bradykinin. It is the most direct...
CH50 Complement Test: Total Complement Activity, High and Low Levels, and Immune Function
The CH50 complement test measures whether the classical and terminal complement pathways can work together to destroy a target. It is a functional screening...
Common Variable Immunodeficiency Test Panel: IgG, IgA, IgM, Vaccine Response, and Diagnosis
A common variable immunodeficiency test panel evaluates whether the body makes enough antibodies and whether those antibodies respond normally to vaccines. The core findings...