Question

Explain the series of events that occur when there is tissue damage accompanied by the presence of bacteria.

Explain the overall signal transduction that occurs when a cell in the innate system encounters a pathogen.

Answer 1

1)   The immune system responds first to stop the infection to other parts of tissue when we encounter an injury in presence of bacteria. Through the site of injury the bacterial cell enters host body and begin to divide and reach a maximum level at these stage they begin to alter the hosts system and damages host cells for their division. The firs cells to respond the bacterial infection is macrophages they reach this site of infection and stop the bacterial growth by swallowing the bacterial cells by phagocytosis they also causes inflammation reactions which helps in release of water from blood which becomes easier for the removal of bacterial cells. At the same time macrophages releases messenger proteins which communicates with neutrophils and neutrophils reaches the site of infection neutrophils kills all infected hosts and bacterial cells. Macrophages also communicate with dendritic cells on activation of dendritic cells by macrophages, dendritic cells engulfed bacterial cells and show them up on their cell surface. Dendritic cells reaches to lymph nodes and shows up the antigen cells to lymphocytes after which a series of reaction occurs which activate all T helper cells and T memory cells. These cells reach the site of infection and helps in fighting the infection while some T cells activate B cells which helps in producing the antibodies. The antibodies produced by B cells reaches the site of infection and bind to bacterial cells surface and cause the lysis of bacterial cells. Macrophages find it easier to identify the bacterial cells which are attached to antibodies and cause easy lysis of bacterial cells. With the combined effort of all immune cells the bacterial infection is stopped after complete eradication of bacterial cells the immune cells die out by process known as apoptosis.

2) In the innate immune response the leukocytes cells kills the bacterial cells and at the same time the mast cells constrict the blood vessels to stop the blood loss simultaneously they sends signals to send more number of leukocytes ate the site on injury. Neutrophils receives cell signals to degrade bacterial cells. Macrophages with help of calls II MHC molecules lyse the bacterial cells. Macrophages also release chemokines which directs the release of more neutrophils at the site of infection and also causes the fever which helps in the healing with more energy used for the healing process. The site of infection becomes inflamed, red with presence of all cells and becomes painful due to presence of painful receptors. T cells also gets activated when the antigen interacts with the toll like receptors these activated T cell activates B cell cells and also produces CD4 cells which helps in lysis of bacterial cells.