The immune system of humans protects the body by destroying the invading foreign particles or micro-organisms. There are various cells that make up the immune system like T cell, B cell, macrophages and neutrophils etc. There are various mechanisms by which these cells recognise the foreign particles and defend the body. The lymphocytes like B cell are very critical to immune system. They have a surface receptor which they bind to the antigen and destroy it. The B cell even produces specific antibodies that are targeted to the antigen to destroy it but only after when the T cell gives the signal to B cell. The lysosomes eat up the small bacterial cells and then destroy them with various toxic enzymes present in them. This is why lysosomes are called “Suicidal Bags”.

The typhoid causing bacteria “Salmonella typhii” deceives the immune system and defends itself by depleting the enzymes present in lysosomes. The salmonella bacteria when inside the lysosome secrete a protein that stops the transport of the essential enzymes from the carriers to the lysosomes. Thus lysosomes lose its potential to kill the bacteria and become helpless. The bacteria then exploit these lysosomes for their nutrients by feeding on the enzymes they contain.

It is a great discovery and will prove effective in developing drugs against these bacteria. But our knowledge of how these bacteria secretes protein and how it works at molecular level still remains a mystery.

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