Development of Immune Cells

Question 1

What cells are formed from the Myeloid lineage?

What cells are formed from the Lymphoid lineage?

Where do the T cells mature? What do they become?

Where do the B cells mature? What do they become?

Answer 1

• Granulocytes (Mast cells, Eosinophils etc.) and APCs (Macrophages, Dendritic cells)
• B and T Lymphocytes, NK cells
• Thymus → Naive T cells
• Bone marrow → Naive B cells

Question 2

LYMPHOCYTE MATURATION:
What are the lymphocytes tested for here?

What are the stages here?

What occurs if they fail to express a Pre-antigen receptor?

What occurs if there’s Weak antigen recognition?

What occurs if there’s Strong antigen recognition?

What occurs if there’s No antigen recognition?

Answer 2

• Their ability to recognise foreign antigens (useful) and respond to self-antigens (not useful + dangerous)
• Proliferation → Pre-antigen receptor expression → Proliferation → Antigen receptor expression → Positive/Negative selection
• Cell death
• Positive selection
• Negative selection → Cell death
• NO positive selection → Cell death by neglect

Question 3

T cell Maturation and Selection:
What do T cells recognise?

What leads to positive selection of CD4+ cells?

B cell Maturation and Selection:
What do B cells recognise?

What occurs if there’s Weak Ag recognition?

What occurs if there’s Strong Ag recognition?

What occurs if there’s No Ag recognition?

When Ag recognition is Strong, what gives the B cell a 2nd chance of survival? What’s this called?

Answer 3

• MHC I and II
• Weak MHC II recognition
• Weak MHC I recognition
• Antigens (Ags)
• Positive selection of Mature B cells
• Negative selection → Cell death
• NO positive selection → Cell death by neglect
• They have an ability to rearrange their receptors to try and reduce this recognition strength = RECEPTOR EDITING

Question 4

SELF/IMMUNOLOGICAL TOLERANCE:
What does Self Tolerance mean?

Why is this needed?

What does Failure of this lead to?

When and Where does Central Tolerance occur?
→ What type of T and B cells are affected here?

When and Where does Peripheral Tolerance occur?
→ What type of T and B cells are affected here?
→ Why is this important?

Answer 4

• Mechanisms that prevent immune responses to self-antigens
• Random generation of Ag receptors on T/B cells can produce self-reactive lymphocytes, which have access to immune cells
• Autoimmunity
• During lymphocyte development in Central lymphoid organs (Bone, Thymus)
  → IMMATURE T and B cells
• When lymphocytes respond to Ags in Peripheral lymphoid organs or tissues
  → MATURE T and B cells
  → Some self-reactive T cells escape Central tolerance