tuberculosis lymphocytes

[nurmd01]

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Why does lymphocytes increase in tuberculosis? The patogen in tuberculosis is a bacteria- mycobacterium tuberculosis- why doesnt neutrophils increase instead?

 

[Transposony]

Why does lymphocytes increase in tuberculosis? The patogen in tuberculosis is a bacteria- mycobacterium tuberculosis- why doesnt neutrophils increase instead?

Mycobacteria are intracellular pathogens. So, it causes a TH1 response --> IFN gamma --> Macrophage activation --> Granuloma
IOW Cell-Mediated Immunity ( Macrophages, CD8+ cytotoxic T cells, NK cells) deals with intracellular pathogens.
Same goes with other facultative intracellular pathogens like Listeria, Histoplasma, Leishmania etc
Obligate intracellulars pathogens like viruses, rickettsiae, and chlamydiae are killed by cytotoxic T cells, natural killer cells, ADCC.

 

[nurmd01]

Thank you Transposony for the clear explanation

 

[worldbeater]

Nice explanation, yeah it's a cell mediated response. Cell mediated is also associated with IL-2, in addition to IF-alpha.

 

[Phloston]

Mycobacteria are intracellular pathogens. So, it causes a TH1 response --> IFN gamma --> Macrophage activation --> Granuloma
IOW Cell-Mediated Immunity ( Macrophages, CD8+ cytotoxic T cells, NK cells) deals with intracellular pathogens.
Same goes with other facultative intracellular pathogens like Listeria, Histoplasma, Leishmania etc
Obligate intracellulars pathogens like viruses, rickettsiae, and chlamydiae are killed by cytotoxic T cells, natural killer cells, ADCC.

Why does lymphocytes increase in tuberculosis? The patogen in tuberculosis is a bacteria- mycobacterium tuberculosis- why doesnt neutrophils increase instead?

Transposony has made a good point about the macrophage-T-lymphocyte "loop" that is exceedingly HY on Step 1.

Alveolar macrophage phagocytoses bacterium --> secretes IL-12 --> stimulates Th0 cells to become Th1 cells (and as Transposony has pointed out IL-12 also stimulates NK cells) --> Th1 cells secrete IFN-gamma --> increased macrophage activation --> cycle continues.

So macrophage --> IL-12 --> Th1 cell activation --> IFN-g --> more macrophage activation.

I was under an ICU consultant a few months ago who randomly asked me how Listeria is killed. Answer is increased CD8+ response (was an answer to a UWorld question since Listeria is facultative intracellular).

 

[worldbeater]

I was under an ICU consultant a few months ago who randomly asked me how Listeria is killed. Answer is increased CD8+ response (was an answer to a UWorld question since Listeria is facultative intracellular).

Yes! Listeria is one of those weird bugs that is gram+, but still has a cell mediated response. Also in another question, they try to treat it with a cephalosporin, but the correct answer is ampicillin. I kept screwing up those two questions until recently.

Also the CD marker for a macrophage is CD14, not CD8 or CD4, like I was expecting.