T lymphocytes

Question 1

T lymphoctes general information

Answer 1

♣ Important component of specific immunity
♣ Through random rearrangement of gene sequences, each T cell recognizes only one specific antigen
• If infection occurs with something that displays this antigen, the antigen will be presented by a major histocompatibility protein complex on the surface of the antigen-presenting cell which indicates the corresponding T cell should perform its function
♣ Most T cells created are deactivated and undergo apoptosis because they either will not react with the MHC or because they react too well and would attack self-cells
♣ Each T cell can only respond to one specific antigen
♣ Even though many are destroyed, there still remain enough to defend the body against almost any pathogens

Question 2

MHC I

Answer 2

• Cytotoxic T (Tc) cells (aka CD8+ T cells as they contain the CD8 protein) recognize and respond to antigens presented by the MHC I complex
• these complexes come from cells infected with viruses or developing tumors
o signal Tc to destroy those cells

Question 3

MHC II

Answer 3

• T helper (Th) cells (aka CD4+ cells) recognize and respond to antigens presented on MHC II
o Activated Th cells release cytokines to stimulate the immune response
♣ Causes other white blood cells to mature and attack

Question 4

Natural Killer T Cells

Answer 4

behave like Tc and Th cells but respond to antigens on other types of cells

Question 5

Memory T Cells

Answer 5

• Once a reaction has occurred, memory T cells reactive to the antigen are formed and remain in circulation for long periods of time
o Allowing a quicker response upon reinfection

Question 6

Regulatory or Repressor T cells

Answer 6

• Have the opposite effect of memory T cells

Tone down the T cell response to self-cells or following an infection

Question 7

♣ T cells begin in bone marrow
• T lymphocyte precursor cells are formed
o They travel via bloodstream to thymus where they mature
• Once maturation is complete, they are released into the lymph to perform their immune functions
♣ T cells are a vital component to the immune system
• Patients with AIDS have low levels of certains types of T cells
Therefore they are more susceptible to infection because their immune system is so weakened

Answer 7

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