¾ Cough: One of the earliest and most common symptoms, present in 40–80% cases ¾ Sputum: Initially not productive, but becomes

Immune Response

Much of the immune response of the host is through

cell mediated immunity (CMI). It is also responsible for

much of the pathology associated with tuberculosis. The

activated lymphocytes and macrophages release cytokines

and gamma interferon.

Serological Response

There are many mycobacterial antigens against which

serological response is produced by the host.

List of mycobacterial antigens

¾ A60

¾ MTB 48

¾ 38KDa

¾ LAM

¾ 16KDa

¾ ESAT –1

¾ L4 – PIM

¾ 19KDa

¾ 14KDa

¾ Antigen 85 complex.

Virulence Factors

The bacteria do not possess the typical bacterial virulence

factors such as toxins, capsules and fimbriae. Many structural

and physiological properties contribute to the virulence.

Slow intracellular growth: It is an effective means of

evading the immune system. Once phagocytosed, it can

inhibit phagosome-lysosome fusion.

Slow generation time: Because of the slow generation

time, the immune system may not readily recognize the

bacteria or may not be triggered to eliminate them.

High lipid concentrations in cell wall: This accounts for

impermeability and resistance to ant microbial agents,

resistance to killing by acidic and alkaline compounds.

Cord factor: It is primarily associated with virulent strains

of bacteria. It is known to be toxic to mammalian cells.

Clinical Manifestations

Tuberculosis is usually classified as pulmonary or

extrapulmonary. Before the recognition of HIV, more than

80% of all cases were limited to the lungs. However, up to

two-third of HIV infected patients with tuberculosis may

have both pulmonary and extrapulmonary disease or

extrapulmonary disease alone.

Pulmonary Extrapulmonary

Pulmonary Pleural TB

tuberculosis TB lymphadenitis

TB pericarditis

TB meningitis

Skeletal TB

Clinical Manifestation of Pulmonary TB

¾ Cough: One of the earliest and most common

symptoms, present in 40–80% cases

¾ Sputum: Initially not productive, but becomes

productive indicating tissue necrosis

¾ Fever: Present in 65–80% of patients. In patients with

advanced stage of disease, fever persists even after

initiation of therapy

¾ Pleuritic chest pain

¾ Dyspnea

¾ Hemoptysis

¾ Chills/sweats

¾ Fatigue/malaise

¾ Anorexia/weight loss.