This reaction is called "delayed hypersensitivity" because it is mediated by sensitized CD4+ T lymphocytes which process antigens in association with class II HLA molecules and release lymphokines.
The lymphokines promote a reaction (especially mediated through macrophages) beginning in hours but reaching a peak in 2 to 3 days.

Hypersensitivity reactions with this mode of action include:

• Granulomatous diseases (mycobacteria, fungi)

• Tuberculin skin reactions

• Transplant rejection

• Contact dermatitis

Cytotoxic T lymphocyte (CTL) mediated responses: CD8+ T cells are generated and lyse specific cells. Class I HLA molecules play a role. Reactions with this mode include:

• Neoplastic cell lysis

• Transplant rejection

• Virus-infected cell lysis

Explanation of Each Option:

1. Sputum examination: This is the primary method for diagnosing active pulmonary tuberculosis. Sputum samples are collected and examined for the presence of Mycobacterium tuberculosis through microscopy (e.g., acid-fast bacilli staining) and culture methods. It is considered the gold standard for confirming active TB cases.

2. Mantoux test: Also known as the tuberculin skin test, this test is used to determine if a person has been exposed to the tuberculosis bacteria. However, it does not diagnose active TB; rather, it indicates whether a person has been infected with the bacteria at some point.

3. Chest X-ray: While chest X-rays are important for identifying lung abnormalities associated with tuberculosis and can support the diagnosis, they are not definitive for detecting the bacteria itself. They are often used in conjunction with sputum examination.

• Definition: Coagulase is an enzyme produced by certain bacteria, most notably Staphylococcus aureus. It catalyzes the conversion of fibrinogen (a soluble plasma protein) into fibrin (an insoluble protein), leading to the clotting of blood.
• Function: The production of coagulase is a virulence factor for Staphylococcus aureus, as it helps the bacteria evade the host's immune system by forming a protective clot around the bacterial cells. This clot can shield the bacteria from phagocytosis and other immune responses.
• Clinical Relevance: Coagulase is used in laboratory tests to differentiate between pathogenic Staphylococcus aureus (coagulase-positive) and non-pathogenic staphylococci (coagulase-negative).

2. Proteolytic Enzymes:

• Definition: Proteolytic enzymes, also known as proteases or peptidases, are enzymes that catalyze the breakdown of proteins into smaller peptides or amino acids by cleaving the peptide bonds between amino acids.
• Function: These enzymes play crucial roles in various biological processes, including digestion, protein turnover, cell signaling, and immune responses. They are found in many organisms, including humans, where they are involved in the digestion of dietary proteins in the stomach and small intestine.
• Types: Proteolytic enzymes can be classified based on their mechanism of action (e.g., serine proteases, cysteine proteases, aspartic proteases, and metalloproteases) and their substrate specificity.

Wenmycin is an antibiotic that is derived from the bacterium Streptomyces wenyangensis. It belongs to the class of compounds known as macrolide antibiotics, which are characterized by their large lactone ring structure. Wenmycin has been studied for its antimicrobial properties, particularly against certain types of bacteria.