Communicable diseases, disease prevention and the immune system GapFill

If the primary defences of an organism (such as blood clotting as a result of  phenolskeratinocytesneutrophilsplatelets) fail to prevent the entry of foreign pathogens, the immune system can recognise and respond to them in a number of ways.  T killer cellsMemory cellsPhagocytesPlasma cells ingest and destroy any pathogens they encounter using enzyme-containing vesicles called  lysosomespeptosomesantisomesnucleosomes, and plasma cells secrete  vaccineslymphocytesantitoxinsantibodies into the blood; each has two binding sites that are complementary to a specific  bacteriumantigenvectortoxin, and a mass of them can be cross-linked together by  opsoninsantitoxinscytokinesagglutinins. T lymphocytes respond to antigen-presenting cells as:

 PainkillersAntifungalsVaccinesAntibiotics containing small quantities of antigens can be administered to individuals as a protective measure to prepare their immune system for a specific disease via the production of antibodies. For example, they could protect against  malariaringwormtuberculosismeningitis, a disease of the lungs caused by bacteria. If enough individuals in a population do this, the population may achieve herd immunity, whereby it is difficult for the disease to spread as there are not enough susceptible individuals. Otherwise, the spread of a disease worldwide has the potential to create  a pandemican inflammatory diseaseclonal expansionan epidemic.