Serology/Immunology 679 are detected in about 30% of the patients suffering from Crohn’s disease. Interestingly, people in contact with

 

IgA antibodies easily form complexes with antigen and are

at the origin of inflammatory processes in various organs.

IgA antibodies are readily detected in the serum of some

apparently healthy individuals at risk, in the sputum of some

patients suffering from a pulmonary tuberculous infection

and in biological fluids of patients suffering from extrapulmonary infections. In particular, specific IgA antibodies

Serology/Immunology 679

are detected in about 30% of the patients suffering from

Crohn’s disease. Interestingly, people in contact with

these patients only show elevated IgG antibodies. Note

that the presence of anti-A 60 antibodies in those patients

is probably due to secondary mycobacterial infections, as

other studies do not report their presence and as nucleic

acids specific to mycobacteria have never been discovered

in that type of patient.

Principle of the Method

Anda-Tb is an immunoenzymatic test with dosage on

a solid phase. Samples of diluted human sera, sputum

(IgA) or cerebrospinal fluid (CSF) are distributed in the

wells of the microtitration plates coated with the A60

mycobacterial complexes. Their incubation allows for the

formation of antigen-antibodies complexes. The unbound

components of the sera are eliminated by washing. The

wells are thereafter incubated with peroxidase-labelled

anti-human IgA, IgG or IgM antibodies that bind to the

antibody complexes present. The unbound antibodies

are eliminated by washing. A solution of tetra-methylbenzidine (TMB) containing hydrogen peroxide, is

thereafter introduced in the wells. A color develops during

the reaction of peroxidase with TMB, whose quantity is

proportional to that of specific antibodies present in the

sample.

For IgA and IgG tests, a reference curve is constructed

by plotting the optical densities of the references. The

concentration of the unknown sera analyzed at the

same time as the references is then determined from the

reference curve and transformed into relative sero-units,

which allows the user to take into account the inevitable

daily variations which occur during the determinations.

For IgM tests, a threshold value is determined from the

optical density obtained with a positive reference. The

sample whose optical density is equal to or greater than

this value is considered positive.

The controls included in the IgG tests are intended to

verify if the test was properly carried out. They are not to

be used as references.

The method employed is a standard ELISA technique.

TUMOR MARKERS

Definitions of Terms

Tumor

A swelling or enlargement occurring in inflammatory

conditions.

Neoplasm

A new growth of tissue characterized by uncontrolled

proliferation of cells.

Cancer

An abnormal growth or swelling.

Metastasis

Spread of cancer from the site of origin to another site

through blood or lymph.

Benign Tumor

A tumor that does not harm the body.

Malignant Tumor

A tumor that can threaten a person’s life.

Tumor Marker

A substance present in or produced by a host in response

to the presence of tumor.