IMMUNE ELEMENTS IN BLOOD

IMMUNE ELEMENTS IN BLOOD

■In response to an infection,WBC count may increase or decrease
●LEUKOCYTOSIS-an increase in WBC count occur.e.g meningitis,pneumococcal pneumonia, appendicitis, gonorrhoea and many types of bacterial infection
●LEUKOPENIA-decrease in WBC count occur .e.g.- salmonellosis ,brucellosis and some viral and rickettisial infections
●LEUKOCYTOSIS or LEUKOPENIA is dected by DIFFERENTIAL WBC COUNT which is a calculation of different types of white blood cells in a sample of 100 white blood cells.


■Leukocytes are of 2 types namely GRANULOCYTES and AGRANULOCYTES
although both contain granules but granules of granulocytes are large enough to be visible under light microscope after staining
But granules of agranulocytes cant be seen under light microscope after staining .


■BLOOD CELLS AND THEIR FUNCTIONS
●RBC-transports oxygen and carbon di oxide
●PLATELETS-blood clotting

WBC-:(GRANULOCYTES )
●Neutrophiles-phgocytosis
●Basophils-inflammation and allergy (production of histamine)
●Eosinophiles-killing of parasites by producing toxic substances
●Dendritic cells-initiation of adaptive immune response and phagocytosis
(AGRANULOCYTES )-:
●Monocytes -phagocytosis on maturation in to macrophage
●Lymphocytes (T cells,B cells, natural killer cells)
●Natural killer cells- destroy target cells by cytolysis and apoptosis
●TCells- cell mediated immunity
●B cells-humoral immunity (antibodies)

IMORTANT NOTES:
■Eosinophiles have little phagocytic activity....they mainly act on parasites like helminths....because they are very small in relation to helminths to ingest and destroy them... they attach to the outer surface of parasites and discharge peroxide ions to destroy them.


■Agranulocytes are responsible for swelling of lymph nodes during an infection.
It occurs due to maturation and proliferation of macrophages and lymphocytes.


■Natural killer cells DON'T KILL MICROBES....they ONLY KILL TARGET CELLS .
Natural killer cells bind to infected host cells. They release granules containing PERFORIN which forms channel in the plasma membrane of target cells and lead to cytolysis due to flow of extracellular fluid in it.
Second type of granules contain GRANZYMES which are protein digesting enzymes and induce the cell to undergo apoptosis.
Due to cell burst, MICROBES (may or may not be intact) are released and then killed by PHAGOCYTOSIS