HOW DOES OUR IMMUNE SYSTEM FIGHT OFF VIRUSES AND BACTERIAS?When our bodies face an attack from an infection they enter a defensive state known as “the immune response.” The immune system in the human body is responsible for recognizing the cells that make up our body from the harmful cells such as viruses. The immune system consists of many different cells, tissues and organs. The workhorse cells of the immune system are the white blood cells. Our bodies generate approximately a billion of them every day in our bone marrow.

WHAT ARE WHITE BLOOD CELLS? WHAT MAKES THEM SO SPECIAL??

WHITE BLOOD CELLS CAN:• INGEST PATHOGENS AND DESTROY THEM• PRODUCE ANTIBODIES THAT DESTROY PATHOGENS• PRODUCE ANTITOXINS THAT WILL NEUTRALISE THE

TOXINS THAT ARE RELEASED BY PATHOGENS

WHITE BLOOD CELL INGESTING DISEASE CAUSING BACTERIA

A PATHOGEN IS A BACTERIUM, VIRUS OR OTHER MICROOGANISM THAT CAN CAUSE DISEASE

WHITE BLOOD CELLS ( ALSO CALLED LEUKYTES) PROTECT THE BODY FROM INFECTION. THERE ARE TWO MAIN TYPES OF WBC, THE NEUTROPHIL AND THE LYMPHOCYTE. THE NEUTROPHIL IS THE “IMMEDIATE RESPONSE” CELL WHICH ACCOUNTS FOR APPROXIMATELY 55-70 PERCENT OF THE TOTAL HUMAN WBC COUNT. THEY GENERALLY LIVE FOR LESS THAN A DAY, SO BONE MARROW MUST CONSTANTLY MAKE NEW NEUTROPHILS TO MAINTAIN PROTECTION AGAINST INFECTIONS.THE LMYPHOCYTE IS ANOTHER MAJOR TYPE OF WHITE BLOOD CELL. THERE ARE TWO MAIN POPULATIONS OF THESE CELLS, T LYMPHOCYTES AND B LMPHOCYTES. T LYMPHOCYTES HELP REGULATE THE FUNCTIONS OF OTHER IMMUNE CELLS AND ATTACK THE INFECTED CELLS AND TUMORS DIRECTLY. B LYMPHOCYTES MAKE ANTIBODIES. THESE ARE PROTEINS THAT TARGET A SPECIFIC BACTERIA, VIRUS AND ANY OTHER FOREIGN CELL.

DON’T FORGET ABOUT RED BLOOD CELLS!RED BLOOD CELLS ARE THE MOST ABUNDANT CELL IN THE BLOOD, ACCOUNTING FOR ABOUT 45% OF ITS CUMULATIVE VOLUME. ITS PRODUCTION IS CONTROLLED BY ERYHTHROPOIETIN, A HORMONE PRODUCED BY KIDNEYS. RBC START AS IMMATURE CELLS IN THE BONE MARROW AND AFTER ABOUT SEVEN DAYS THEY MATURE AND RELEASE INTO THE BLOODSTREAM. RED BLOOD CELLS HAVE NO NUCLEUS UNLIKE MANY OTHER CELLS. THIS ALLOWS THEM TO EASILY CHANGE SHAPE, ALLOWING THEM TO FIT THROUGH THE DIFFERENT BLOOD VESSELS IN OUR BODIES. HOWEVER THIS LIMITS THE LIFE OF THE CELL AS IT TRAVELS THROUGH THE SMALLEST BLOOD VESSELS, DAMAGING THE CELLS MEMBRANE AND DEPLETING ITS ENERGY SUPPLIES. THIS IS A REASON WHY THE RBC ONLY SURVIVES ON AVERAGE 120 DAYS.

RED BLOOD CELLS CONTAIN A SPECIAL PROTEIN CALLED HEMOGLOBIN WHICH HELPS CARRY OXYGEN FROM THE LUNGS TO THE REST OF THE BODY, RETURNING CARBON DIOXIDE FROM THE BODY TO THE LUNGS, WHICH IS LATER EXHALED.

DID YOU KNOW THAT BLOOD APPEARS RED BECAUSE OF THE LARGE AMOUNT OF RED BLOOD CELLS, WHICH GET THEIR COLOR FROM THE HEMOGLOBIN?

THE DIFFERENT TYPES OF WHITE BLOOD CELLS

Basophils are comprised of less than 1 percent of the total white blood cell count, they play an integral role in promoting blood flow and preventing coagulation. Basophils circulate the bloodstream and release two important chemicals at the tissue site: heparin and histamine. Heparin is an anti-coagulant that prevents blood cells from clotting too quickly and histamine is a vasodilator commonly released during allergic reactions to increase blood flow. These two molecules work together to quickly increase the availability of other immune system cells at the site of infection or inflammation.

THE DIFFERENT TYPES OF WHITE BLOOD CELLS

Neutrophils which we have previously covered, are the non-specific immune cells. They are the first line of defense against the invading antigens and are first to arrive at the site of infection or injury. They are short lived and self-destruct after engulfing harmful antigens.

THE DIFFERENT TYPES OF WHITE BLOOD CELLS

Monocytes comprise 2 to 8 percent of the total population of circulating WBC. They originate in the bone marrow and develop into large macrophages in the bloodstream. They are the largest white blood cells and are held responsible for engulfing cell debris, waste and harmful bacteria. Macrophages attack microbes by extending pseudopodia (feet like extensions) around the cells and then destroy the microbe by releasing enzymes from inside the macrophage.

THE DIFFERENT TYPES OF WHITE BLOOD CELLS

Eosinophils, sometimes known as acidophils, defend the body against multicellular parasites and moderate allergic reactions. They develop in the bone marrow before migrating out into the bloodstream. Eosinophils combat foreign parasites and particles, releasing chemical meditators in a process called degranulation. Small granules inside the eosinophils are released to destroy the foreign invaders. The harmful chemicals are reactive proteins such as peroxides, nucleases and lipases.