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MCAT Bio > Immune System > Flashcards

Immune System Flashcards

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1
Q

Strategies of the immune system

A
  1. Phagocytose invaders

2. Secrete effector molecules that combat invaders

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2
Q

Innate immunity

A

–quick and nonspecific

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3
Q

acquired (adaptive) immunity

A
  • -develops more slowly and only after the body has experienced the initial attack
  • -slow and specific
  • -B-cell mediated and T-cell mediated
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4
Q

Parts of innate immunity

A
  1. skin as a barrier
  2. stomach acid and digestive enzymes
  3. phagocytosis cells such as neutrophils and macrophages
  4. chemicals in the blood
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5
Q

agents of inflammation

A
  • -histamine
  • -prostaglandins
  • -lymphokines
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6
Q

“First responders” in innate immune response

A
  1. macrophages (phagocytosis) - can engulf as many as 100 bacteria
  2. neutrophils (phagocytosis) - can engulf 5-20 bacteria
  3. monocytes - mature to become macrophages in the tissue
  4. eisinophils and basophils - related to neutrophils
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7
Q

pus

A

–composed of dead neutrophils and macrophages that die after engulfing bacteria and dead tissue

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8
Q

eosinophils and basophils

A
  • -innate immune cells related to neutrophils
  • -eosinophils work mainly against parasitic infections
  • -basophils release many of the chemicals of the inflammation reaction
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9
Q

diapedesis

A

–the method by which neutrophils and monocytes enter the tissue (from the circulation)

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10
Q

key feature of acquired immune system

A

–immunological memory

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11
Q

B-cell immunity

A
  • -a branch of acquired immune system
  • -called “humoral” or “antibody-mediated immunity”
  • -cannot act against invading substances that have already made their way into cells
  • -promoted by B-lymphocytes
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12
Q

T-cell immunity

A
  • -a branch of the acquired immune system

- -also called “cell-mediated immunity”

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13
Q

B lymphocytes

A
  • -differentiate and mature in the adult bone marrow and the fetal liver
  • -promote antibody mediated immunity
  • -Each B-lymphocyte makes a single type of antibody
  • -Displays an antibody on its membrane and the antibody is called a B-cell receptor
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14
Q

immunoglobulin

A

antibody

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15
Q

antigen

A

the foreign particle

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16
Q

antigen-antibody recognition

A

–the process by which an antibody recognizes a foreign particle

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17
Q

primary response

A
  • -the immune response that results from the first exposure to an antigen
  • -BCR recognizes the appropriate antigen
  • -B-lymphocyte, assisted by a helper T-cell, differentiates into plasma cells and memory B-cells
  • -memory B-cells proliferate and remain in the body
  • -plasma cells and memory b-cells can be called upon to synthesize antibodies in the case of re-infection - secondary response
  • -primary response requires about 20 days to reach its full potential
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18
Q

plasma cells

A
  • -can survive for decades or even a lifetime

- -after they are differentiated from B-lymphocyte, begin synthesizing free antibodies and releasing them into the blood

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19
Q

secondary response

A
  • -when plasma cells and memory B-cells are activated to make antibodies in the case of a re-infection
  • -requires about 5 days to reach its full potential
20
Q

Antibody functions

A
  1. Mark the antigen for phagocytosis by macrophages and natural killer cells
  2. Bind and then begin a cascade of reactions involving blood proteins that cause the antigen-bearing cell to be perforated
  3. Cause antigenic substances to agglutinate, precipitate, or even may block a toxin’s chemically active portion
  4. Free antibodies may attach their bases to mast cells. When an antibody bound to a mast cell also binds to an antigen, the mast cell releases histamine and other chemicals.
21
Q

T-cell immunity

A
  • -cell mediated immunity
  • -effective against cells that have already been infected b/c it is not restricted to free-floating substances the way antibody-mediated immunity is
  • -T-lymphocytes have an antibody-like protein (T-cell receptor) at its surface that recognizes antigens
  • -T-lymphocytes never make free antibodies
22
Q

T-cell response

A
  • -TCR recognizes the appropriate antigen
  • -T-lymphocytes differentiate into helper T-cells, memory T-cells, suppressor T-cells, and killer T-cells (cytotoxic T-cells)
  • -helper T-cells assist in activating B-lymphocytes
  • -helper T-cells activate activate other types of T-lymphocytes including killer and suppressor T-cells
23
Q

suppressor T-cells

A

–play a negative feedback and regulatory role in the immune system

24
Q

Killer T-cells

A
  • -bind to the antigen-carrying cell and release perforin, a protein that punctures the antigen-carrying cell
  • -Can attack many cells b/c they do not phagocytize their victims
  • -Do not themselves die when they kill invading pathogens like macrophages and neutrophils
  • -responsible for fighting some forms of cancer and for attacking transplanted tissue
25
Q

Major Histocompatibility Complex

A
  • -MHC molecules are displayed on the surface of all cells except those that do not contain nuclei
  • -Function to display antigens for recognition
26
Q

MHC 1

A
  • -display antigens derived from intracellular pathogens such as viruses and some bacteria
  • -Since all cells can be infected by these pathogens, all nucleated cells have MHC class 1 molecules
27
Q

MHC 2

A
  • -display antigens derived from extracellular pathogens

- -These pathogens must be phagocytksed, so MHC class 1 molecules are displayed by phagocytic cells

28
Q

Professional Antigen Presenting cells (APCs)

A
  • -cells that phagocytose extracellular bacteria or other pathogens in order to display their antigens
  • -macrophages, dendritic cells, some B-cells
29
Q

exogenous pathway

A

–the process by which these antigens are processed and displayed by MHC class 2 molecules on the cell surface

30
Q

How are B-cells and T-cells activated?

A
  • -Need two signals: Signal 1 and Signal 2

- -After BOTH signals have been received, B-cells and T-cells are activated

31
Q

Signal 1

A

–when the BCR or TCR recognizes its appropriate antigen

32
Q

Signal 2

A
  • -B-cells and T-cells receive it when there is an active infection
  • -called the “danger signal”
33
Q

How do T cells receive signal 1?

A
  • -professional APCs engulf a pathogen, process antigens via the exogenous pathway, and display antigenic determinants on the MHC class 2 molecules on their surfaces
  • -T-cell recognizes the combination of MHC and antigen, which provides Signal 1 via TCR stimulation and downstream signaling
34
Q

How do T cells receive signal 2?

A

–provided by components of the innate immune system in response to infectious insults by circulating cytokines or up-regulation of membrane-bound surface proteins

35
Q

How do B cells receive signal 1?

A

–when a free floating antigen cross-links multiple BCRs on the same cell

36
Q

How do B cells receive signal 2?

A

–provided by helper T-cells

37
Q

clonal selection

A

–the process by which B-cells and T-cells are selected for. That is, B-cells and T-cells that do not appropriately recognize a foreign antigen undergo apoptosis (positive selection) and those that inappropriately attack self-tissue also undergo apoptosis (negative selection)

38
Q

Site of T-cell clonal selection

A

thymus

39
Q

Site of B-cell clonal selection

A

bone marrow

40
Q

How many antibodies exist for a single antigen?

A

ONE

41
Q

How many antibody types does a single B-lymphocyte produce?

A

ONE

42
Q

Blood type A

A
  • -displays A antigens on cell surface
  • -makes antibodies against B antigens
  • -Accepts blood type A and blood type O
43
Q

Blood type B

A
  • -displays B antigens on cell surface
  • -makes antibodies against type A antigens
  • -accepts blood type B and blood type O
44
Q

Blood type O

A
  • -does not display any antigens on cell surface
  • -Makes antibodies against type A and type B
  • -accepts only blood type O
45
Q

Rh factor

A
  • -Rh factors are a surface protein on red blood cells
  • -Rh-negative means you do not have the marker
  • -Rh-positive means you do
46
Q

Rh factor and pregnancy

A
  • -If the mother is Rh-negative and she has an Rh-positive baby, it is not typically a problem for the fetus during the first pregnancy
  • -During birth of the first child, however, the mother is exposed to the baby’s blood and the mother then makes antibodies against Rh-positive blood
  • -If the mother gets pregnant with another Rh-positive baby, her immune system can attack it and kill the baby
47
Q

megakaryocyte

A
  • -made in bone marrow

- -giant cells that split up into platelets and are responsible for clotting function

MCAT Bio (6 decks)

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