L3 Immunology

Question 1

write a note on T cells (helper/cytotoxic)

Answer 1

helper cells: has CD4 on cell surface which helps recognition of antigens on APCs. these cells activate Macrophages, DCs and Cytotoxic T and B cells

Cytotoxic cells: have CD8 marker, these kill infected cells. are similar to NK cells hwoever they need “education” and activation

Question 2

write a note on B cells

Answer 2

differentiate into plasma cells that produce antibodies. 5 types of antibodies = IgM, IgA, IgG, IgE, IgD

functionality requires coordination from T cells

Question 3

what is the functiond of the 5 antibody types

Answer 3

IgM = non specific (shaped like star)
IgA= serum and mucosal
IgG= systemic (blood and lymphatics- highest level in serum)
IgE = allergy or parasite
IgD = for B cell development

Question 4

what is the process of dendritic cells carruing antigen to the lymph nodes?

Answer 4

1. immature dendritic cells reside in the peripheral tissues
2. they migrate via lymphatic vessels to regional lymph nodes
3. mature dendritic cells activate the naive T cells in the lymphoid organs

Question 5

how do T helper cells help B cells to become Plasma cells

Answer 5

1. activated follicular B cells express CCR7 and migrate to the T/B boundary (in areas i.e peyers patches)
2. the activated T cells express CXCR5 and reduce CCR7 expression, and migrate towards B cells
3. B cells recieve the help and differentiate into memory B cells or plasma blasts (go to bone marrow to mature)

Question 6

explain how B cells can encounter antigens in the lymphatic system

Answer 6

1. antigens enter the lymph node via afferent lymphatics at the subacapsular sinus
2. the antigens are captured by macrophages present here and are presented to B cells
3. antigens are transported to follicular dendritic cells and presented to B cells for affinity maturation