Lecture 13 Flashcards Preview

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Flashcards in Lecture 13 Deck (26):
1

All our cells have

unique surface markers (1000s molecules)

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MHC-I molecules are built into

cell membrane of all cells except red blood cells

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MHC-II markers seen only on

membrane of antigen presenting cells (macrophages, B cells, thymus cells)

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Function of complex antigens:

-T cells recognize is problem
-will display as part of their MHC-II

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Pathways of Antigen Processing:

-B and T cells must recognize a foreign antigen before beginning their immune response
-B cells can bind to antigen in extracellular fluid
-T cells can only recognize fragments of antigens

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Foreign antigen in body fluid is phagocytized by

APC

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Antigen is digested and fragments are

bound to MHC-II molecules stuck into antigen presenting cell membrane

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APC migrates to

lymphatic tissue to find T cells

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Cytokines & Cytokine Therapy:

1. Small protein hormones involved in immune responses
2. Cytokine therapy uses cytokines (interferon)

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Cell-Mediated Immunity:

Begins with activation of T cell by a specific antigen
Result is T cell capable of an immune attack

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Types of Mature T Cells

Helper T cells
Cytotoxic (killer) T cells
Memory T cells

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Helper T Cells:

1. Display CD4 on surface so also known as T4 cells or TH cells
2. Recognize antigen fragments associated with MHC-II molecules & activated by APCs
3. Function is to costimulate all other lymphocytes

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Cytotoxic T Cells:

1. Display CD8 on surface
2. Known as T8 or Tc or killer T cells
3. Recognize antigen fragments associated with MHC-I molecules
4. Costimulation required by cytokine from helper T cell

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Memory T Cells:

1. T cells from a clone that did not turn into cytotoxic T cells during a cell-mediated response
2. Available for swift response if a 2nd exposure should occur

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Antibody-Mediated Immunity:

-Millions of different B cells that can recognize different antigens and respond
-B cells sit still and let antigens be brought to them
-Once activated, differentiate into plasma cells that secrete antibodies
-Antibodies circulate in lymph and blood

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Antibody Classes:

IgG
IgM
IgD
IgA
IgE

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IgG =

80% of plasma Ab’s, enhances phagocytosis, neutralizes viruses, protects newborn

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IgM =

10% of plasma Ab’s, first produced during infection, neutralizes bacteria, agglutinates

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IgD =

0.2% of plasma Ab’s, D = Don’t know

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IgA =

15% of plasma Ab’s, only mucosal surfaces

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IgE =

0.002% of plasma Ab’s, allergic reactions

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Immunological Memory:

-Primary immune response
-Secondary immune response with 2nd exposure

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Primary immune response:

first exposure to antigenresponse is steady, slow
memory cells may remain fordecades

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Secondary immune responsewith 2nd exposure

1000’s of memory cells proliferate & differentiate into plasma cells & cytotoxic T cells
recognition & removal occurs so quickly not even sick

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T cells must learn to recognize

self (its own MHC molecules ) & lack reactivity to own proteins

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T cells mature in thymus:

those can’t recognize self or react to it
same for b-cells