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Infectious diseases are caused by -> Pathogens
*To identify thousands of pathogens we use the Koch´s postulates
1. The pathogen must be present in the animal that has the disease
2. The pathogen, then, is isolated and grown in the laboratory
3. The pathogen is injected in a healthy organism
4. Then the pathogen, from the second animal, is isolated and grown in the laboratory. It should be the same pathogen as the pathogen first extracted from the first animal.
Pathogens can spread to humans in 5 ways: air, food, water, person-to-person contact and a bite from animals.
First Line Of Defense
1. Mucous membranes———> Mucus ———> lysozymes ———-> enzymes that destroy bacterias (destroys the membrane of the pathogen)
*The Mucus traps Pathogens in:
Respiratory system, Digestive system, Urethra and the Vagina
Skin have pores that release:
Sweat, oil (help take out pathogens) and waxes (ear)
Pathogens clot the pore and a pimple is formed because oil cant go out.
Second Line of Defense
A. Inflamatory Response:
*Histamine (substance that make capillaries permeable)
*Phagocyte (destroy pathogens)
*Neutrophil (most abundant type of phagocyte, can squeeze through capillary walls to reach infection)
* Macrophage(type of phagocyte that engulf pathogens )
*Natural Killer cells(W.B.C that attack pathogen-infected cells, not the pathogens themselves)
B. Temperature Response(sweat, shivering)
–Fever: rise of the body temperature above 37° C, means body is responding to an infection.
C.Proteins: complement system (made up of 20 different of proteins, they eliminate the infected cells) and interferon (protein released from an infected cell causing nearby cells to make a protein that help him resist the infection).
Specific Defenses (third line of defense)
The immune system: cells and tissues that recognize and attack foreign substances in the body.
*Tissues of the I.S: bone marrow (make lymphocytes), lymph vessel, lymph nodes (contain lymphocytes), adenoids, tonsils, spleen (largest lymphatic organ, store R.B.C and make lymphocytes), thymus (make special kind of lymphocyte).
*W.B.C of the I.S called: lymphocytes
*2 types of lymphocytes: B cell (made and mature in the bone marrow) and T cell (made in Bone Marrow but mature in the thymus)
Inflammation: any damage to tissue cause inflammation:
Bacteria enters; Plasma proteins get out from the vessel, Plasma proteins marks the bacteria; The W.B.C engulf the bacterias
*Immune response: reaction of the body against an antigen
Cell mediated response
Macrophage engulf a virus and sends viral antigens
T cells receives the viral antigens and binds to them causing the macrophage to reléase interlukin-1
Interlukin-1 activates helper T cells and they start to reléase interlukin-2
Interlukin-2 stimulates división of helper T cells and activates cytotoxic T cells
Cytotoxic T cells destroy infected cells and other become memory T cells
Supressor T cells help to shut down the immune response after the pathogen is destroyed
Humoral immune respons
Macrophage engulf a virus and sends viral antigens
T cells receives the viral antigens and binds to them causing the macrophage to reléase interlukin-1
Interlukin-1 activates helper T cells and they start to reléase interlukin-2
B cells actívate by the reléase of interlukin-2 and begin to multiply
Some become memory B cells and other plasma B cells
Plasma cells make antibodies and they bind to antigen to mark them for destruction.
Primary Inmune Response(first time having the disease)
Antigen enters; effector cells(kill) made; memory cells made (memorize the disease, dont attack)
Secondary Inmune Response: Antigen enters; memory cells reproduce quicker into effector cells (in bigger amount than last time) and memory cells (in bigger amount than last time) and it is erradicated easier. Produce antibodies faster. Except: Cold and Flu ( their external protect coat mutate)
Vaccination: introduction of antigents into the body to cause immunity. Memory cells memorize the vaccine (the antigen) and in the second immune response is easier to erradicate it. Sometime vaccines doesn´t work okay and they need a booster to be sure the immune system recognize the pathogen. Examples of vaccines for: Polio, measles, tetanus.
Immune deficiency:Inmune system doesn’t work well. 2 ways to have Immune deficiency: acquired with a virus or been born with it.
Autoimmune diseases:The system attacks its own body thinking the body is the invasor. To treat this you take immunosupressors to mantain it stable. Ex: arthritis (attack the joints)
*HIV virus: enter a host cell and make a copy of the DNA*
ASTHMA: extra mucus lines in the airways and dont permit to breath well.