Tuberculosis and Granuloma Overview

Granuloma

• Granuloma is a chronic specific inflammation.
• It's an organized collection of macrophages and inflammatory cells around a pathogen.
• The immune system forms a granuloma when it can't eliminate a pathogen.
• Granulomas lead to necrosis and tissue replacement by fibrosis.

Tuberculosis

• Tuberculosis is a chronic, infectious granuloma caused by Mycobacterium tuberculosis.
• Methods of infection include inhalation of TB from an active patient or ingestion of contaminated milk.

Host Bacteria Interaction in Tuberculosis

• M. tuberculosis replicates inside macrophages.
• Macrophages typically present antigens to lymphocytes for immune response. In tuberculosis, macrophages fail to do so.
• Bacteria can become dormant, leading to latent infection.
• Successful antigen presentation by macrophages to lymphocytes triggers an immune response, producing cytokines and resulting in tissue necrosis.

Risk Groups and Symptoms

• Risk factors for tuberculosis include AIDS, overcrowding, malnutrition, close contact with active patients, smoking, and alcohol use.
• Common symptoms include chronic cough (sometimes with blood), fever, night sweats, and weight loss.
• "Consumption" is a historical term that refers to weight loss due to tuberculosis.

Tubercle (Tuberculous Granuloma)

• A tubercle is the fundamental unit of tuberculosis.
• It's a microscopic structure comprising chronic inflammatory cells, caseous necrosis, and fibrosis around tubercle bacilli.
• Tubercles represent the body's reaction to T.B bacilli.

Mechanisms of Caseation (Causes)

• Hypersensitivity reactions between T lymphocytes' lymphokines and tubercule bacilli antigens (tuberculoprotein) can cause caseation necrosis.
• Ischemic necrosis can result from endarteritis obliterans.

Immune Reaction Against TB

• Early stage (0-3 weeks): M. tuberculosis multiplies unchecked. Mannose-capped glycolipid and mannose receptors are involved.
• Later stage (>3 weeks): Activated macrophages, IFN-γ, TNF, and chemokines are involved, leading to caseous necrosis, monocyte recruitment, and granuloma formation (epithelioid giant cells, lymphocytes).

Primary Tuberculosis

• Ghon's focus is the primary site of infection.
• Tuberculosis infects the lymph nodes, causing a primary complex (infection, central caseous necrosis, and epithelioid macrophages).
• The triad consists of a Ghon's focus, tuberculous lymphangitis, and tuberculous lymphadenitis in regional lymph nodes.

Secondary Pulmonary Tuberculosis

• This is a reinfection or reactivation of tuberculosis.
• Key features include apical cavitation, absence of lymph node involvement, and potential complications like hemoptysis (coughing up blood), pneumothorax (air in the pleura), right-sided heart failure (due to lung fibrosis), and amyloidosis (insoluble protein deposition).

Intestinal Tuberculosis

• Primary intestinal tuberculosis comprises a primary intestinal complex, tubercles at Peyer's patches, TB ulcers, tuberculous lymphangitis, and tabes mesenterica.
• Secondary intestinal tuberculosis involves tubercles in Peyer's patches of the terminal ileum, characterized by multiple ulcers with undermined edges, soft caseous floors, and a healing process through fibrosis.
• Lymph nodes aren't involved in secondary intestinal tuberculosis.

Tuberculous Peritonitis

• This is a secondary type of tuberculosis common in children.
• Types include wet/ascetic (exudative reaction) and dry/adhesive (proliferative reaction leading to tubercle formation).

Pott's Disease

• A secondary tuberculosis infection of the spine.
• Causes include secondary infection from the bloodstream.
• Sites include the cervical, thoracic, and lumbar regions.
• Key features include kyphosis (spinal curvature), abscess formation, and paraplegia (paralysis).

This quiz explores the concepts of granulomas and tuberculosis, including their definitions, formation, and impact on the immune system. You will learn about the interactions between Mycobacterium tuberculosis and host macrophages, as well as symptoms and risk factors associated with this chronic infection.