THE IMMUNE SYSTEM
THE IMMUNE SYSTEM
• NONSPECIFIC DEFENSES AGAINST INFECTION
INCLUDE THE
– SKIN
– MUCOUS MEMBRANES
– PHAGOCYTIC CELLS
– ANTIMICROBIAL PROTEINS
THE IMMUNE SYSTEM
• NONSPECIFIC DEFENSE MEANS THAT THEY
DON’T DISTINGUISH BETWEEN MICROBES
– THE SKIN IS THE FIRST LINE OF DEFENSE
– THE RESPIRATORY AND DIGESTIVE SYSTEMS ARE
OPEN TO THE ENVIRONMENT; LINED
WITH MUCUS TO
PREVENT BACTERIAS
(MICROBES) FROM
ENTERING
THE IMMUNE SYSTEM
• NONSPECIFIC DEFENSE MEANS THAT THEY
DON’T DISTINGUISH BETWEEN MICROBES
– IF MICROBES DO ENTER THE BODY CELLS OR
TISSUES THEN
• NEUTROPHILS AND
MONOCYTES
ATTACK FOREIGN BODY
– PHAGOCYTIC CELLS
THE IMMUNE SYSTEM
• NONSPECIFIC DEFENSE MEANS THAT THEY DON’T
DISTINGUISH BETWEEN MICROBES
– IF MICROBES DO ENTER THE BODY CELLS OR TISSUES THEN
• NEUTROPHILS AND
MONOCYTES
ATTACK FOREIGN
BODY
– MACROPHAGES
» LARGE
MONOCYTES
THAT WANDER
ACTIVELY
THROUGH
INTERSTITIAL
FLUID
THE IMMUNE SYSTEM
• NONSPECIFIC DEFENSE MEANS THAT THEY DON’T
DISTINGUISH BETWEEN MICROBES
– IF MICROBES DO ENTER THE BODY CELLS OR TISSUES
THEN
• NEUTROPHILS AND MONOCYTES ATTACK FOREIGN BODY
– NATURAL KILLER CELLS  ATTACK CANCER CELLS AND INFECTED
BODY CELLS
– INTERFERONS  PROTEINS PRODUCED BY VIRUS-INFECTED
CELLS THAT HELP OTHER CELLS RESIST VIRUSES (VIRUS INFECTION
ACTIVATES INTERFERON GENE)
– COMPLEMENT PROTEINS  COAT SURFACES OF MICROBES TO
EASE PHAGOCYTOSIS, CUT HOLES IN MICROBE MEMBRANE, OR
AMPLIFY INFLAMMATORY RESPONSE
THE IMMUNE SYSTEM
• THE INFLAMMATORY RESPONSE MOBILIZES
NONSPECIFIC DEFENSE FORCES
THE IMMUNE SYSTEM
• INFLAMMTORY RESPONSE
– MAJOR COMPONENT OF OUR NONSPECIFIC DEFENSE
SYSTEM
– DAMANGED CELLS RELEASE CHEMICAL ALARM
SIGNALS LIKE HISTAMINE
• DILATES THE BLOOD VESSELS MAKING THEM LEAKIER
– CHEMICALS SPARK THE MOBILIZATION OF VARIOUS
DEFENSES
– THE WHITE BLOOD CELLS GATHERED IN THE AREA
ENGULF THE BACTERIA AND THE REMAINS OF ANY
DAMAGED OR DEAD CELLS
THE IMMUNE SYSTEM
• INFLAMMATORY RESPONSE
– HELPS PREVENT SPREAD OF INFECTION BY
RELEASING CLOTTING FACTORS
– INFLAMMATORY RESPONSE MAY BE LOCALIZED
OR WIDESPREAD (EX. FEVER)
– WIDESPREAD INFLAMMATION CAN BE
DANGEROUS
• SEPTIC SHOCK  BACTERIAL INFECTION THAT BRINGS
ABOUT OVERWHELMING INFLAMMATORY RESPONSE
THE IMMUNE SYSTEM
• THE LYMPHATIC SYSTEM BECOMES A CRUCIAL
BATTLEGROUND
DURING
INFECTION
THE IMMUNE SYSTEM
• LYMPHATIC SYSTEM
– CONSISTS OF A BRANCHING NETWORK OF
VESSELS, NUMEROUS LYMPH NODS (SAC-LIKE
ORGANS PACKED WITH THE WHITE BLOOD CELLS
CALLED LYMPHOCYTES), THE TONSILS AND
ADENOIDS, THE APPENDIX AND THE SPLEEN
THE IMMUNE SYSTEM
• LYMPHATIC SYSTEM
– ALSO INCLUDES THE BONE MARROW AND THYMUS
(SITES WHERE WHITE BLOOD CELLS DEVELOP)
– 2 MAIN FUNCTIONS
• RETURN TISSUE FLUID TO THE CIRCULATORY SYSTEM
• FIGHT INFECTION
– LYMPH
• FLUID CARRIED IN THE LYMPATHIC VESSELS; SIMILAR TO
INTERSTITIAL FLUID BUT LESS OXYGEN AND NUTRIENTS
– **SWOLLEN GLANDS ARE THE RESULT OF LYMPH
NODES MAKING EXTRA LYMPHOCYTES TO FIGHT
INFECTION
THE IMMUNE SYSTEM
• THE IMMUNE RESPONSE COUNTERS SPECIFIC
INVADERS
– IMMUNE SYSTEM  RECOGNIZES AND DEFENDS
AGAINST INVADING MICROBES AND AGAINST CANCER
CELLS
– ANTIGEN  A MOLECULE THAT ELICITS AN IMMUNE
REPONSE
– ANTIBODY  A PROTEIN FOUND IN BLOOD PLASMA
THAT ATTACHES TO ONE PARTICULAR KIND OF
ANTIGEN AND HELPS COUNTER ITS EFFECTS
THE IMMUNE SYSTEM
• THE IMMUNE RESPONSE COUNTERS SPECIFIC
INVADERS
– IMMUNE SYSTEM HAS A REMARKABLE
“MEMORY”; ONCE IT ENCOUNTERS AN ANTIGEN
IT REMEMBERS IT AND CAN COMBAT IT VERY
QUICKLY
– IMMUNITY  RESISTANCE TO SPECIFIC INVADERS
THE IMMUNE SYSTEM
• IMMUNITY  RESISTANCE TO SPECIFIC INVADERS
– CAN BE ACQUIRED NATURALLY OR BY VACCINATION
• VACCINE 
HARMLESS
VARIANT OF A
DISEASECAUSING
MICROBE
– STIMULATES
THE IMMUNE
SYSTEM TO
MOUNT
DEFENSES
AGAINST THE
VARIANT
THE IMMUNE SYSTEM
• IMMUNITY
– 2 FORMS
• ACTIVE IMMUNITY
– BODY IS STIMULATED TO PRODUCE ITS OWN ANTIBODIES
• PASSIVE IMMUNITY
– BODY IS GIVEN ANTIBODIES (NOT PERMANENT!!)
» EXAMPLES INCLUDE:
FETUS GETS FROM MOTHER; A DIRECT SHOT OF
ANTIBODIES
THE IMMUNE SYSTEM
• LYMPHOCYTES
MOUNT A
DUAL DEFENSE
– LYMPHOCYTES
• WHITE BLOOD
CELLS THAT
SPEND MOST
OF THEIR TIME
IN THE TISSUES
AND ORGANS
OF THE
LYMPATIC SYSTEM
THE IMMUNE SYSTEM
• B CELLS
– ARISE FROM IMMATURE LYMPHOCYTES THAT
DEVELOP IN THE BONE MARROW
– GIVE RISTER TO
HUMORAL
IMMUNITY
• IMMUNITY
OCCURING IN THE
BODY FLUIDS
THE IMMUNE SYSTEM
• T CELLS
– ARISE FROM IMMATURE LYMPHOCYTES THAT
DEVELOP IN THE THYMUS
– GIVE RISE TO CELL-MEDIATED IMMUNITY
• ATTACKS INFECTED CELLS
• ANTIGEN RECEPTORS
– MOLECULES
CAPABLE OF
BINDING TO A
SPECIFIC TYPE OF
ANTIGEN
THE IMMUNE SYSTEM
• CLONAL SELECTION MUSTERS DEFENSIVE
FORCES AGAINST SPECIFIC ANTIGENS
– CLONAL SELECTION
• ATTACHMENT OF AN
ANTIGEN TO A SPECIFIC
LYMPHOCYTE CAUSES
MULTIPLICATION OF THAT
LYMPHOCYTES VIA MITOSIS
THE IMMUNE SYSTEM
• THE INITIAL IMMUNE RESPONSE RESULTS IN A
TYPE OF “MEMORY”
– IT TAKES TWO EXPOSURES TO AN ANTIGEN TO
MOUNT THE STRONGEST IMMUNE RESPONSE
THE IMMUNE SYSTEM
• THE INITIAL IMMUNE RESPONSE RESULTS IN A
TYPE OF “MEMORY”
– PRIMARY IMMUNE RESPONSE
• OCCURS WHEN LYMPHOCYTES ARE FIRST EXPOSED TO AN
ANTIGEN AND FORM A CLONE OF EFFECTOR CELLS
– SECONDARY IMMUNE RESPONSE
• AFTER PRIMARY; SECOND EXPOSURE ELICITS FASTER,
STRONGER RESPONSE
– MEMORY CELLS
• MADE AT SAME TIME AS EFFECTOR CELLS; DIFFER IN
STRUCTURE AND FUNCTION; MAY LAST FOR DECADES
THE IMMUNE SYSTEM
• OVERVIEW: B CELLS ARE THE MAIN WARRIORS OF
HUMORAL IMMUNITY
– PLASMA CELLS
• ANOTHER NAME FOR EFFECTOR B CELLS, THE ONES PRODUCING
ANTIBODIES
• ANTIBODIES ARE THE WEAPONS OF HUMORAL
IMMUNITY
– ANTIBODY HAS 2 RELATED FUNCTIONS
• RECOGNIZE AND BIND TO CERTAIN ANTIGENS
• ASSIST IN NEUTRALIZING THE ANTIGEN
– ANTIGEN-BINDING SITE
• REGION OF THE MOLECULE RESPONSIBLE FOR THE ANTIBODY’S
RECOGNITION-AND-BINDING FUNCTION
THE IMMUNE SYSTEM
• ANTIBODIES MARK ANTIGENS FOR
ELIMINATION
– ANTIBODIES BIND TO FORM ANTIBODY-ANTIGEN
COMPLEX WHICH ALLOWS
FOR ANTIGEN
DESTRUCTION
THE IMMUNE SYSTEM
• MONOCLONAL ANTIBODIES ARE POWERFUL
TOOLS IN THE LAB AND CLINIC
– MONOCLONAL ANTIBODIES
• ALL THE CELLS PRODUCING
THE ANTIBODIES ARE
DESCENDANTS OF A SINGLE
CELL AND THEREFORE ARE
IDENTICAL
• GREAT PROMISE IN
MEDICINE AND RESEARCH
THE IMMUNE SYSTEM
• T CELLS MOUNT THE CELL-MEDIATED
DEFENSE AND AID HUMORAL IMMUNITY
– 2 MAIN KINDS OF T CELLS
THE IMMUNE SYSTEM
• T CELLS MOUNT THE CELL-MEDIATED
DEFENSE AND AID HUMORAL IMMUNITY
– 2 MAIN KINDS OF T CELLS
• CYTOTOXIC T CELLS
– ATTACK BODY CELLS THAT ARE INFECTED WITH PATHOGENS
• HELPER T CELLS
– HELP ACTIVATE CYTOTOXIC
T CELLS AND MACROPHAGES,
EVEN HELP STIMULATE B CELLS
TO PRODUCE ANTIBODIES
THE IMMUNE SYSTEM
• T CELLS MOUNT THE CELL-MEDIATED DEFENSE
AND AID HUMORAL IMMUNITY
– CYTOTOXIC T CELLS
• ATTACK BODY CELLS THAT ARE INFECTED WITH PATHOGENS
• CTYOTOXIC T CELLS BIND TO ANTIGEN
• WHEN BOUND IT CAUSES THE PRODUCTION OF PERFORIN
– PROTEIN THAT CUTS HOLES IN MEMBRANE
– ALLOWS OTHER
PROTEINS TO
ENTER AND
CAUSE DEATH
OF ANTIGEN
THE IMMUNE SYSTEM
• T CELLS MOUNT THE CELL-MEDIATED
DEFENSE AND AID HUMORAL IMMUNITY
– CYTOTOXIC T CELLS
• MAY HELP PREVENT CANCER
• MONITOR CELLS AND DESTROY CANCEROUS ONES
• IT’S A MYSTERY
WHY THEY
STOP WORKING
THE IMMUNE SYSTEM
• T CELLS MOUNT THE CELL-MEDIATED
DEFENSE AND AID HUMORAL IMMUNITY
– HELPER T CELLS
• HELP ACTIVATE CYTOTOXIC
T CELLS AND MACROPHAGES,
EVEN HELP STIMULATE B CELLS
TO PRODUCE ANTIBODIES
THE IMMUNE SYSTEM
• THE IMMUNE SYSTEM DEPENDS ON OUR
MOLECULAR FINGERPRINTS
– MAJOR HISTOCOMPATIBILITY COMPLEX (MHCs)
• GROUP OF SELF-PROTEIN GENES
• PROTEINS FOUND ON OWN CELLS; MARK THEM AS
“OFF-LIMITS” TO IMMUNE SYSTEM
THE IMMUNE SYSTEM
• MALFUNCTION OR FAILURE OF THE IMMUNE
SYSTEM CAUSES DISEASE
– AUTOIMMUNE DISEASES
• RESULTS WHEN THE IMMUNE SYSTEM GOES AWRY
AND TURNS AGAINST THE BODY’S OWN MOLECULES
(EXAMPLE = LUPUS)
THE IMMUNE SYSTEM
• MALFUNCTION OR FAILURE OF THE IMMUNE
SYSTEM CAUSES DISEASE
– IMMUNODEFICIENCY DISEASES
• LACK ONE OR MORE COMPONENTS OF THE IMMUNE
SYSTEM, AND ARE SUSCEPTIBLE TO INFECTIONS THAT
ORDINARILY WOULD NOT CAUSE A PROBLEM
(EXAMPLE = HODGKIN’S; AIDS)
THE IMMUNE SYSTEM
• ALLERGIES ARE OVERREACTIONS TO CERTAIN
ENVIRONMENTAL ANTIGENS
– ALLERGIES
• ABNORMAL SENSITIVITIES TO ANTIGENS IN OUR
SURROUNDINGS
THE IMMUNE SYSTEM
• ALLERGIES ARE OVERREACTIONS TO CERTAIN ENVIRONMENTAL
ANTIGENS
– ALLERGENS
• ANTIGENS THAT CAUSE ALLERGIES
– MAST CELLS
• NORMAL BODY CELLS THAT PRODUCE HISTAMINE AND OTHER CHEMICALS
THAT TRIGGER THE INFLAMMATORY RESPONSE
– ANTIHISTAMINES
• DRUGS THAT INTERFERE WITH HISTAMINE’S
ACTION AND GIVE TEMPORARY RELIEF
FROM AN ALLERGY
– ANAPHYLACTIC SHOCK
• VERY SEVERE (POSSIBLY FATAL) ALLERGIC
REACTION
• CAN BE COUNTERED WITH AN INJECTION OF
EPINEPHRINE (ADRENALINE)
THE IMMUNE SYSTEM
• AIDS LEAVE THE BODY DEFENSELESS
– HIV DESTROYS THE HELPER T CELLS; TURNING OFF
HUMORAL AND CELL MEDIATED IMMUNE
RESPONSES
– LEAVES THE BODY DEFENSELESS AND OPEN TO
OPPORTUNISTIC INFECTIONS
– AIDS DOESN’T KILL, OPPORTUNISTIC INFECTIONS
DUE
THE IMMUNE SYSTEM
• SOME THINGS THAT ARE BAD FOR US; OR THAT ARE
NOT SUPPOSED TO BE INSIDE OF US, ARE THE RESULT
OF CHEMICAL (METABOLIC) REACTIONS IN
OUR CELLS…OUR
IMMUNE SYSTEM
CAN’T BE
RESPONSIBLE FOR
THESE
• WE NEED THE
EXCRETORY
SYSTEM!!!