[anti- + -gen]
SEE: autoantigen; SEE: cytokine; SEE: histocompatibility locus antigen

antigenic (ant″i-jen′ik), adj.
antigenically (ant″i-jen′ĭ-k(ă-)lē), adv.
antigenicity (ant″i-jĕ-nis′it-ē), n.

allogeneic antigen


alpha-fetoprotein antigen

SEE: alpha-fetoprotein.

Australia antigen

Australian antigen A term formerly used for hepatitis B surface antigen.

bladder tumor antigen

ABBR: BTA A protein released into the urine by malignant cells in the bladder, studied as a possible marker of cancer of the urinary bladder. Because of the low prevalence of bladder cancer and the low positive predictive value of the test, the test is not currently recommended for use.

cancer antigen

Cancer Antigens Used as Tumor Markers

Antigen Name or DesignationAbbreviationThe Tumor It Detects or Monitors
Alpha-fetoproteinAFPNonseminomatous germ cell tumor
CA 15-3Breast cancer
CA 19-9Pancreatic cancer
CA 27-29Breast cancer
CA 50Gastrointestinal tract tumors
CA 125Ovarian/peritoneal cancer
CalcitoninMedullary cancer of the thyroid gland
Carcinoembryonic antigenCEAGastrointestinal tract tumors and tumors of solid internal organs
CD 20Non-Hodgkin lymphoma
Cytokeratin fragment 21-1Lung cancer
Estrogen receptorERBreast cancer
HE4Ovarian cancer
Human chorionic gonadotropinHCGNonseminomatous germ cell tumors; choriocarcinoma
Human epidermal growth factor receptor 2HER2/neuBreast and gastric cancers; adenocarcinoma of the gastroesophageal junction
ImmunoglobulinsMultiple myeloma; Waldenstrom macroglobulinemia
Microglobulin-beta 2 subunitb2-MMultiple myeloma
Neuron-specific enolaseNSEBroad variety of cancers, including small-cell carcinoma of lung
NY-BR-40 and othersBreast cancer
Prostate specific antigenPSAProstate cancer
ThyroglobulinThyroid cancer
Urinary tumor associated antigenUTAAMelanoma

carcinoembryonic antigen


CD antigen

SEE: cluster of differentiation

class I antigen


class II antigen

Any of the major histocompatibility molecules present on immunocompetent cells.

cross-reacting antigen


D antigen

SEE: Rh blood group.

glutamate dehydrogenase antigen

ABBR: GDH antigen An antigen found in the cell wall of Clostridium difficile a common cause of infectious diarrhea. It is released by the bacterium into stool. Its presence in stool is an indication of active infection.

H antigen


hepatitis antigen


hepatitis B core antigen

SEE: hepatitis B e antigen; SEE: hepatitis B surface antigen

hepatitis B e antigen


hepatitis B surface antigen

SEE: hepatitis B core antigen; SEE: hepatitis B e antigen

hepatitis C core antigen


high-frequency antigen

In transfusion medicine, any red blood cell surface antigen that does not belong in any known blood group system but can cause antibody-mediated transfusion reactions, lung injury, or hemolytic disease in the newborn.

histo-blood group antigen

Any of the major antigens on blood cells implicated in transfusion reactions.

histocompatibility locus antigen



The identification of HLA sites on chromosome 6 has enabled researchers to correlate the presence of specific histocompatibility and certain autoimmune diseases, e.g., insulin-dependent diabetes mellitus, multiple sclerosis, some forms of myasthenia gravis, rheumatoid arthritis, and ankylosing spondylitis.

SYN: SEE: human leukocyte antigen
SEE: major histocompatibility complex

human leukocyte antigen

SEE: Histocompatibility locus antigen

H-Y antigen


K antigen


leukocyte common antigen

A protein found in the cell membranes of various white blood cells, including basophils, granulocytes, lymphocytes, macrophages, plasma cells, and thymocytes, among others.

lymphogranuloma venereum antigen

An antigen used in a skin test for lymphogranuloma venereum.

mumps skin test antigen


nuclear antigen


O antigen


oncofetal antigen

SYN: SEE: oncofetal protein

onconeural antigen


p24 antigen

The core protein of HIV. The presence of p24 antigen in the blood is a marker of uncontrolled HIV replication. p24 antigenemia is encountered in the acute retroviral syndrome before host immune response and in advanced AIDS when the immune system has been destroyed. When p24 antigen is detected in the blood, the HIV viral load is high and the person is highly infectious.

proliferating cell nuclear antigen


prostate-specific antigen

ABBR: PSA A nonspecific marker of abnormalities in the prostate gland, including prostatic infection, inflammation, and prostate cancer. PSA circulates in the blood and can be detected by blood tests. PSA levels have been used to screen for prostate cancer, but are neither sensitive nor specific for detecting the disease.
Descriptive text is not available for this imageElevations in PSA levels may prompt invasive testing (such as with biopsies) that may detect indolent cancers as well as aggressive ones. Side effects of prostate biopsy include urinary incontinence and erectile dysfunction.

SEE: prostate cancer.

protective antigen


soluble antigen

SEE: T cell.

soluble liver antigen

A liver antigen detectable in the serum of some patients with autoimmune hepatitis but not usually in patients with chronic viral hepatitis or hepatitis caused by exposure to toxic drugs.

squamous cell carcinoma antigen

ABBR: SCCAg A tumor marker found in many patients with cancers of the breast, cervix, head and neck, liver, lung, and skin. Tests to detect SCCAg help determine the prognosis and management of these malignancies.

T-dependent antigen


thymus-dependent antigen


thymus-independent antigen


T-independent antigen

ABBR: TI Either of two types of antigens that stimulate B-cell production of antibodies without the presence of T cells. TI-1 antigens, e.g., lipopolysaccharides from gram-negative organisms, stimulate production of both specific (monoclonal) and nonspecific (polyclonal) antibodies and promote the release of cytokines from macrophages that enhance the immune response. TI-2 antigens, which result in monoclonal antibody production, may require the presence of cytokines.
SEE: B cell; SEE: T cell

transplantation antigen


tumor-specific antigen


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