Multiple mycobacterial antigens in diagnostic tuberculins

Area of Science:

• Immunology
• Microbiology
• Allergy

Background:

• Mycobacterial antigens are crucial for tuberculosis diagnosis.
• Different tuberculin preparations (Old Tuberculin, PPD) are used, but their specificities are not fully elucidated.
• Guinea-pig antisera with IgG1 antibodies were generated against various mycobacterial components.

Purpose of the Study:

• To investigate the antigenic composition of different tuberculin preparations.
• To compare the specificities of immune responses elicited by Old Tuberculin (OT) and purified protein derivative (PPD) tuberculins.
• To understand the nature of delayed-type hypersensitivities in response to mycobacterial antigens.

Main Methods:

• Preparation of guinea-pig antisera containing IgG1 antibodies against mycobacterial antigens.
• Passive cutaneous anaphylaxis (PCA) assays using these antisera and mycobacterial antigens.
• Intravenous injection of diagnostic tuberculins into sensitized animals to assess antigen presence and relative amounts.
• Analysis of antigenic profiles of OT and PPD tuberculins prepared using different methods (ammonium sulfate, TCA, benzoic acid).

Main Results:

• PPD-S contains five distinct antigens, with one dominant antigen.
• A dominant antigen in PPD is absent in Old Tuberculins.
• The dominant antigen in OT is absent in TCA-precipitated PPD but present in ammonium sulfate-precipitated PPD.
• Diagnostic testing with OT detects a delayed-type sensitivity distinct from that detected by TCA-PPD.

Conclusions:

• Diagnostic tuberculin testing involves multiple, distinct delayed-type hypersensitivities.
• The preparation method of tuberculin significantly influences its antigenic composition and diagnostic specificity.
• Understanding these specificities is crucial for accurate tuberculosis diagnosis and interpretation of immune responses.