Chronic Inflammation,Granulomatous Dieases,Tuberculosis Pathology Lecture Note

Chronic inflammation

•Chronic Suppurative on acute:

•Chronic granulomatus: (Initiates without an acute phase)

Suppurative in type:

•Abscesses

Inadequate or delayed drain leads to thick fibrous wall formation.

The residual bacteria get reactivated

Pus formation.

•Presence of foreign material or indigestible dead tissue.

Eg: Osteomyelitis, damaged Collagen

Chronic inflammation

•Follow acute inflammation

Persistence of the stimulus

Disturbance to the healing process

•Repeated bouts of acute inflammation and healing in between.

•Low grade persistent infection.

Definition

Prolong process in which destruction and acute inflammation proceeds together with the healing process.

Causes

•Sequelae of an acute inflammation

•Foreign bodies

•Microorganisms where body can mount limited immune reactions

•Impaired body defense

•Immune reactions

Chronic inflammation without an acute phase

•Infection: TB, Leprosy, Syphilis

•Immunological: Rheumatiod arthritis Ulcerative colitis Crohn’s disease

•Poor bloodsupply (leg ulcer)

Chronic inflammatory lesions

•May vary histologically according to causative agent

•However there is a set of morphological features in common.

Histologically

•Infiltration by mononuclear cells

Macrophages

lymphocytes

plasma cells

•Proliferation of blood vessels/fibrosis (angiogenesis)

•Fibrosis

•Tissue destruction (induce by inflammatory cells)

Mononuclear phagocytic system

•Blood monocyte:

•Macrophages (at extra vascular tissue)

•Tissue macrophages (Scattered in connective tissue or concentrated in organs)

Eg: Kupffer cells in Liver

Sinus histiocytes in lymph nodes

Alveolar macrophages in lung

Osteoclasts in bones

Microglia (CNS)

Monocytes

•Migration

•Morphological transformation (macrophages and giant cells)

•Activation

•Secretion of biologically active products

Cells types present

•Macrophages

•Lymphocytes

•Eiosenophils

•Mast cells

Existence of CI, AI and repair

•Macrophages persist at the site (Due to the influence of chemical mediators)

•Destruction of invading microorganisms /normal tissues

•Secretion of chemical mediators by macrophages

Functions of them,

Proliferation of fibroblasts, Laying down of collagen

Angiogenesis, Activation of lympho macrophages

· Dead and dieing leukocytes/necrotic tissues helps in developing acute inflammation

Granulomas /Granulomatus infection

•Chronic inflammatory lesion in the form of mass.

•Collection of macrophages or modified macrophages (epitheliod / giant cells)

Granulomas /Granulomatus infection

•A granuloma is a focal area of granulomatus inflammation.

•Consist of macrophage aggregation

•Epithelial cell transformation

•Collar of lymphocytes

•Appearance giant cells and of fibrosis can see with the time

Eg:

•TB

•Sarcoidosis

•Cat scratch disease

•Leprosy

•Syphilis

•Mycotic infections

Two types of granulomas: Base on pathogenesis

•Foreign body type:

Form around foreign bodies

•Immune type: When the foreign practical are capable of induce cell mediate immune responses

(but not always granulomas will develop)

Definition

Granulomas is a result of chronic inflammatory reaction containing a collection of cells of monocytic series arrange in a compact mass.

Cells

•Macrophages

•Epithelioid cells

•Giant cells: Langhans giant cells

Foreign body type giant cells

Accumulation of macrophages

· Under the influence of chemotaxis

C5a, fibrinopeptides, cationic proteins

Lymphokines :

PDGF, TGF(beta)

products of collagen brake down

· By mitotic division

· Immobilization and prolong survival (if the irritants are low virulent )

Tuberculosis

· Chronic disease common worldwide.

· Causes a characteristic granulomatous inflammation

· Inability of the neutrophils to kill the micro organisms due to lipoprotein coating.

· Mycobacterium tuberculosis.

Hominis (lungs)

Bovis (Tonsils, Intestine)

Spread

•Droplet from patients (weeks or months)

•Conjunctiva

•Punctures

•However need sustain contact than casual contact.

Tissue damage

•MT has no Endotoxins

Exotoxins

Histiolitic enzymes

Development of immune response against outer coat of the organism.

Tuberculin test

•2 to 4 weeks after infection : + Tuberculin test

•PPD (purified protein derivative)

(Culture in which TB is grown)

•Induration More that 5.mm within 48 hours.

•Positivity indicates infection but not the disease.

Primary Tuberculosis

•Occurs in individuals who have never previously been infected with M. tuberculosis (childhood infection if TB is common, adult life if uncommon)

•Usually caused by inhalation of the organisms or rarely by ingestion of the organism.

Primary infection

•Lungs Hilum

•Tonsils neck nodes

•Intestine mesentery

Primary Tuberculosis

•In respiratory system, inhalation of the organisms cause a subpleural lesion usually in the lower part of the upper lobe or upper part of the lower lobe. This is called Ghon focus.

•Location is in these sites is because bacterium is a strict aerobe and prefers these well oxygenated regions

Ghon’s focus

· When the tissue is invaded by the mycobacteria there is no hypersensitivity reaction. Instead there is acute, non specific inflammatory response with predominant neutrophils.

· This is followed by macrophages which ingest the bacilli and present Ags to to T lymphocytes leading to proliferation of a clone of T cells .

· The emergence of specific hypersensitivity lead to release of lymphokines,that attract more macrophages.

· These accumulate to form the characteristic granuloma.

Ghon focus

•Usually single

•1 to 2 cm

•Location –Beneath pleura- mid zone of the lung

Primary complex

•Tubercle bacilli, either free or contained in macrophages, may drain to the regional lymph nodes and set up granulomatous inflammation, causing massive lymph node enlargement.

•The combination of the Ghon focus, draining lymphatics and the regional lymph nodes is called the primary complex.

Calcification of the lymph nodes

Microscopic appearance

Sequelae of primary complex

•Healing with small fibrous scar replacing caseous necrosis. Lesion will be walled off.

•Calcification

•Reactivation of infection later when host defences become lowered.

•plural effusion

•Enlarged caseous nodes can obstruct bronchi, leading to collapse, retention of secretion and inflammatory consolidation

•Caseous node erodes into a bronchi with satellite lesions in lungs (TB bronchopneumonia).

•Eroding into a pulmonary vein causing generalised milliary TB.

•Erosion into pulmonary artery leads to miliary TB of lungs

TB bronchopneumonia

· Opening of the caseous node to a bronchus.

· Air bone infection

· TB bronchopneumonia

· (Multiple pneumonic patches arrangeed in and around terminal bronchi)

· The lesions spread rapidly and accumulate macrophages and lymphocytes followed by necrosis

TB bronchopneumonia

•Necrotic patches get enlarged and discharged which will lead to dissemination and cavitations. (no fibrous walls)

•Pneumothorax

•TB bronchopneumonia can happen after both 1ry and 2ry TB.

•Rapidly spreading tuberculous bronchopneumonia: debilitated by intercurrent disease, diabetes, malnutrition etc.

•Acute miliary tuberculosis of the lungs due to blood stream spread to lungs. Grey tubercles visible to naked eye 3mm in diameter. More numerous and larger in upper lobes than lower lobes. Microscopically these are ill formed and often giant cells are absent. Usually these lesions do not cavitate

Effects on the other organs of the body

•Miliary tuberculosis due to systemic spread to kineys, spleen, brain, liver etc.

•Tuberculous ulcers in the intestine due swallowed sputum.

•Tuberculosis of larynx due to direct spread from sputum.

•Secondary amyloidosis.

Miliary TB

•Common with 1ry TB

•Due to involvement of veins

•Multiple scatted tubercles

•Not well developed/uniform in size

•1-2 mm

•Some times without giant cells (necrosis)

•

Secondary Tuberculosis (Post primary)

•Infection may me exogenous or endogenous

•After active primary infection

•Reactivation asymptomatic primary lesions:

Malnutrition,

Severe illness,

Intercurrent lung infection,

Systemic immunosuppression

•Exogenous: caused by inhaled organisms

Immunity

•During primary tuberculosis or during BCG immunisation, the patient develops cell mediated immunity to antigens of tubercle bacillus.

•This is demonstrated by skin test (Mantoux) test

•Immunity is associated with increased resistance to subsequent infection.

Re infected lesions:

•Apex of the lungs

•Endogenous infections (swallowing sputum)

•Metastatic lesions are similar to re-infected

Lesions

•Large in size (spread locally) no lymph node involvement

Cavity formation

•Caseous material discharge gradually leaving a small cavity.

•Cavities can become very large with overgrowth of fibrous tissue.

•Cavity walls are irregular with raised bands representing obliterated blood vessels.

•The surface is lined by caseous material or by pus and debris mixed with blood.

•If the disease is inactive the wall becomes very smooth

· In early cases the lesions are often in the apices of the lungs

· In advanced cases there may be more than one cavitatory lesion.

· All the lesions are distributed in the upper part of the lungs

· Caseation may involve the wall of a bronchus leading to obstruction of the lumen.

Sequelae of tuberculous cavities
Local effects

· Due to fibrosis lung tissue shrinks causing bronchiectasis (upper lobe bronchiectasis)

· Blood vessels can become weaken and rupture leading to haemoptysis

· Aneurysm formation- called Rasmoussen’s aneurism leading to fatal haemorhage.

· Fungal infections can be localized in these cavities.

Acid fast Bacilli

The Mycobacteria

Characteristics of Genus Mycobacterium

· slim rod shaped organisms (1-10 µm long)

· Nonmotile, nonsporing, slow growing obligate aerobes

· cell envelope with a high lipid content, mycolic acids, complex long chain fatty acids

· Acid-fast with Ziehl-Neelson stain

Mycobacterium tuberculosis

· slim (1-4µm), un-encapsulated, strongly acid-fast rod, cigar shaped

· prefers 37⁰ C, 5-10% CO_2, pH 6.0-7.6

· obligate aerobe, slow growth - doubling time 18 h

· requires complex media such as Löwenstein Jensen medium for culture.

· resistant to drying and most disinfectants except for formaldehyde and glutaraldehyde.

· also resistant to highly polar inorganic acids and alkaline solvents.

· UV and heat sensitive. (2 h in the sunlight will kill it. If it is in sputum, 20-30 h are needed)

· multiplies intracellularly in phagosome

· Cell Wall of M. tuberculosis

· The cell envelope also contains peptidoglycan and has a complex glycolipid structure forming the outermost layer.

· Other important components include: lipoarabinomannan, sulfatides, mycolic acid, trehalose 6,6 dimycolate and waxes.

· Virulence Factors

· Cell wall rich in waxes and lipids, especially mycolic acids - serves as LPS.

· Mycolic acid glycolipids and trehalose 6,6 dimycolate (cord factor), - cause granuloma formation in animal tissue.

· Catalase, peroxidase and lipoarabinomannan - help resist the host cell oxidative response.

· Lipoarabinomannan also induces cytokine production.

· Sulfatides and trehalose dimycolate, are toxic to animal models.

Natural History of TB

· M. tuberculosis is acquired through the inhalation of droplets

· If a particle is less than 5µm, it can escape the first line of respiratory defenses

· inhaled droplets containing the organism are engulfed by macrophages.

· Bacteria not initially killed by the macrophage - multiply within.

· When the organisms reach sufficient numbers inside the macrophage is killed, - released organisms are ingested by other macrophages.

· Infected macrophages produce cytokines and chemokines - attract other phagocytic cells -formation of a nodular granuloma - the tubercle.

· Eventual dissemination of bacteria to the lymph and bloodstream

· Immunity is caused by T cell, and not by B cell proliferation.

· Cells involved include: CD4, CD8 T cells and NK cells.

· CMI develops 2-6 weeks after infection and in 90% of people, the infection is aborted without ever having symptoms of disease.

· Less than 10% go on to develop progressive disease.

· Formation of Th1 (type 1) granulomas composed of T cells and macrophages. Macrophages in the granuloma fuse creating Langerhans giant cells.

· Cytokines are produced during this process and include IL-1, IL-12, TNF-alpha and IFN-gamma.

· Hosts that cannot raise a Th1 response will develop miliary tuberculosis.

· Increased risk of disease after primary infection is found in:

· young children,

· HIV infected,

· intravenous drug abusers (IVDA).

· prison inmates, the homeless,

· the elderly

The Tuberculin Test

· The tuberculin test uses the Mantoux method (intradermal injection), and measures DTHR to PPD.

· Positive reaction leads to 10 mm induration after 48-72 h in in a normal individual.

· Positive reaction indicates previous exposure to M. tuberculosis or nontuberculous mycobacteria, including BCG vaccine - tuberculin conversion.

· Negative reaction indicates non-exposure, pre-hypersensitive state, or loss of TB sensitivity from primary infection.

Diagnosis of Tuberculosis

· Ziehl-Neelson stain- showing acid fast bacilli.

· Culture – LJ medium

· Nucleic Acid Assays (NAA)

· Chest x-ray

Prophylaxis

After a positive tuberculin test consists of INH for 6 to 9 months or 4 to 9 months of rifampin.

Bacillus of Calmette and Guerin (BCG)

· 70% effective in preventing infection

· Attenuated Mycobacterium bovis of low virulence is inoculated as vaccine.

Treatment

· Six months of therapy with INH and rifampin plus two other drugs for 6 weeks cures infection in 95% of cases

· First line antituberculosis drugs: INH, rifampin, pyrazinamide, streptomycin, ethambutol

· Second line drugs: para-aminosalicylic acid (PAS), ethionamide, cycloserine, kanamycin, rifabutin, fluoroquinolones

· Combined therapy is employed to avert resistance formation – MDRMT (multi-drug resistant M. tb)

Nontuberculous Mycobacteria (NTM):

General Characteristics

· Found in soil and water

· Non-communicable; no human to human spread.

· Disease from NTMs usually develops in trauma, or immunosuppression.

· acid-fast, INH resistance is common

The Runyon Classification

· classifies NTMs based on pigmentation produced under light and dark conditions and their rate of growth

Photochromogens – R1

slow growing, and produce a yellow-orange pigment when exposed to light.

Ex: M. kansasii

causes lung disease clinically resembling TB, especially in those with preexisting lung conditions such as COPD

antigenically similar to M. tuberculosis.

long, banded, beaded, "barber pole", yellow bacillus due to beta carotene crystals.

M. marinum

causes swimming pool granulomas, and abscesses (fish fancier’s finger).

infects sites of abrasions because the organism likes a lower temperature.

Inhabits both fresh and salt water. It infects a lot of marine organisms.

Scotochromogens- R2

slow growing, and produce a yellow-orange pigment in light or in the dark.

Ex: M. scrofulaceum

Found in water, Enters through oropharynx and draining lymph nodes

produces scrofula, a granulomatous cervical adenitis, usually in children.

Nonchromogenic- R3

slow growing, and do not produce pigment

M. avium intracellulare complex (MAC)

Pleomorphic, at least 30 types, widespread in the environment, but only a few cause disease

Strains that infect immunocompromised hosts - M. avium

Strains that infect immunocompetent hosts - M. intracellulare.

MAC binds and invades oropharyngeal and gastrointestinal cells causing cough, weight loss, upper lobe x-ray changes, and cavities - all similar to TB.

Scrofula, cervical lymphadenitis in children

commonest NTM seen in late AIDS

Rapid Growers- R4

rapid growing mycobacteria (colonies in 5 days). They do not produce pigment.

Ex: M. chelonae and M. fortuitum

Infections occur as complications of surgical procedures - prosthetic implants, mechanical heart valves, contaminated operating equipment, mammoplasty etc.

present as soft tissue infections, lung infections, bone infections, CNS infections, or keratitis in the eye.

highly drug resistant

Mycobacteria not in the Runyon Grouping

Mycobacterium leprae

Un-culturable

grown in armadillos (a natural host) or in mouse footpads (12.5 day doubling time).

Optimal temperature for growth is lower than core body temperature, so it grows on skin and superficial nerves.

lives in macrophages and Schwann cells.

Cell wall contains lipoarabinomannan (LAM) similar to M. tuberculosis, but there is a unique M. leprae-specific phenolic glycolipid (PGL-1).

Causes leprosy, which is also known as Hansen’s Disease.

The incubation period for leprosy is 5-7 years.

Clinically, there are two ends to the spectrum of disease, - tuberculoid and lepromatous leprosy, and gradations in-between.

Tuberculoid leprosy

Granulomas with very few organisms can be seen

Activated CD4+ cells are abundant in the core of the tuberculoid granuloma - produce interferon γ,stimulating macrophages to contain M. leprae growth.

CD4+ cells also secrete IL-2, which results in expansion of the CD4+ cell population.

On the periphery of the granuloma CD8+ cells are present, inhibiting expansion of the granuloma and extensive tissue destruction.

Clinically, tuberculoid leprosy is characterized by anesthetic plaques, and asymmetric peripheral nerve trunk involvement.

Lepromatous leprosy

poor CMI response with large number of organisms.

CD4 and CD8 cells are found throughout the lesion. CD8 cells secrete cytokines that enhances the growth of M. leprae and suppresses CD4 function and expansion.

Granulomas are poorly formed, and macrophages are full of M. leprae. CD4+ cells are present but in much fewer numbers compared to tuberculoid leprosy.

IL-4 appears to be an important cytokine that suppresses CD4+ cell function and proliferation.

Clinically, characterized by symmetric skin nodules, plaques, leonine (i.e., lion-like) facies, loss of eyelashes and body hair, and testicular dysfunction

Lepromatous

Tuberculoid

Mycobacterium ulcerans

Causes Buruli ulcers, the third most common mycobacterial infection

Typically, a single lesion begins as small, painless, subcutaneous nodule - most often on a limb.

In 1 - 2 months, the nodule ulcerates, and enlarges to 15 or more centimeters.

There is no pus, and a biopsy of an ulcerated lesion shows low inflammatory infiltrate.

Skin adjacent to the lesion, and sometimes the whole limb, can become edematous. Ulcer can widen and deepen, destroying adjacent structures and bone.

Treatment: surgical debridement to stop the spreading ulcer

CLASSIFICATION OF MYCOBACTERIA ASSOCIATED WITH HUMAN DISEASE

Mycobacterium	Clinical significance	Pigmentation Growth
Unclassified
M Tuberculosis , M bovis M ulcerans	Strict pathogens	No No
M leprae	Strict pathogen	- -
Runyon Group 1
M marinum , kansasii Runyon Group 2	Usually pathogenic	Photochromogens slow
M scrofulaceum	Rarely pathogenic	Scotochromogens slow
Runyon Group 3
M avium intracellulare	Pathogenic in immunocompromised	No slow
Runyon Group 4
M fortuitum, M chelonae	Rarely pathogenic	No ‘rapid’