Question

Think about a bacterial cell entered the blood stream of a human. State the probable sequence of immunological interactions and responses that will occur in both innate and adaptive immune system and support your answer with molecules, receptors, pathways and cells involved. (200-300 words)

Answer 1

When a foreign bacteria invades the body, there comes the innate and acquired immune resoponses against the body. the innate response is the first attack resposne against the bacteria comprises the white blood cells while the acquired response is a way complex one as in it the body distinguish the foreign cells and kill them by various mechanism . few of the concepts and ways are deescribed below

when bacteria enters the body, the host immune respond with a complement system, consisting of complement proteins, the complement proteins kills bacteria via three pathways, the classical complement , alternative pathwaya and lectin pathway.

in the first classical pathway, there is binding of antibodies on the surface of the bacteria , and antibodies thus becomes target for one particular complement protein complex known as Fc region, and inititiates a cascade of cleavage and reform to form MAC , which is a complex of compplement proteins and generates opsonins which marks the bacterium for destruction.

the alternate complement pathway does not require antibody to initiate lysis of bacteri, here C3 comlex directly binds to the bacteria and activate MAC and thus results into lysis of bacteria

in lectin pathway, MBL, mannan- binding lectin binds to protein containing mannose residues that are found in some type of bacteria and intitiate C3 response,and form MAC and thus lysis

there are other ways too to kill bacteria, and one of them is phagocytosis, the opsonized bacteria which is along with complement protein is recognised by a complement receptor present on phagocytic cell, and this cell engulf the opsonized bacterial cell along with the complement protein and digest it and kills it. this phagocytosis is takes place with the help of helper t cells and recognise the bacterial fragments with the help of cytokines,the t hlper cells, produce interferons and interleukins which promotes humoral immunity and activates B cells and these b cells make antibodies which stick to extracellular bacteria and prevent their growth and kills them

another way is via cell mediated immunity, this works like this, the bacteria attacks and a macrophage get infected by it, now helper t cells will come into action and attaches themselves with the macrophages via their own TCR receptors and bind to the macrophage receptor which is non other than the classii MHC cell,this makes the release of interferons and killing of bacteria

these are few of the ways of immune response and fate of bacteria in human body.