The term complement refers to a set of serum proteins that cooperates with both the innate and the adaptive immune systems to eliminate blood and tissue pathogens. 

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Intracellular bacterial

Intracellular bacterial infections tend to induce a cell-mediated immune response, specifically DTH. 

In this response, cytokines secreted by CD4+ T cells are important—most notably IFN-ϒ, which activates macrophages.

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#Unit 4. Cell Communication and Cell Signaling

Host immune responses and bacterial evasion mechanisms

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Tuberculosis

Tuberculosis, caused by Mycobacterium tuberculosis.

Pulmonary infection usually results from inhalation of small droplets of respiratory secretions containing a few bacilli.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

The inhaled bacilli are ingested by alveolar macrophages in the lung and inhibiting formation of phagolysosomes

CD4+ T cells are activated within 2 to 6 weeks after infection.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

These cells wall off the organism inside a granuloma called a tubercle. The localized concentrations of lysosomal enzymes in these granulomas can cause extensive tissue necrosis.

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Diphtheria

Natural infection with C. diphtheriae occurs only in humans and is spread by respiratory droplets. 

The organism colonizes the nasopharyngeal tract and causes little tissue damage, with only a mild inflammatory reaction.