Structure and Function of Lymphocytes: Topic 1

Question 1

what are lymphocytes?

Answer 1

a type of WBC found primarily in lymphatic organs such as the spleen, tonsils, and lymph nodes

Question 2

what are the three main types of lymphocytes?

Answer 2

T cells
B cells
natural kill cells (NK cells)

Question 3

where do lymphocytes arise from?

Answer 3

All arise from hematopoetic stem cells within the bone marrow

however, each type of lymphocyte matures in a different fashion and has its own function within the body

T cells mature in the thymus while B and NK cells mature in the bone marrow

Question 4

what are T cells and B cells part of?

Answer 4

our adaptive immune system

T cells: cell-mediated immunity

B cells: humoral-mediated immunity

Question 5

what are NK cells part of?

Answer 5

our innate immune system

they respond to and kill virus-infected cells as well as tumor cells

Question 6

To which parts of the immune system do T cells, B cells, and NK cells belong?

Answer 6

T and B cells are part of adaptive immunity, and NK cells are part of innate immunity

Question 7

do B and T cells look different?

Answer 7

normal, unstimulated B and T lymphocytes look identical

to tell them apart, special studies that detect cell surface markers are required

Question 8

what do B and T cell lymphocytes look like?

Answer 8

slightly larger than RBCs

round with a large nucleus and very little cytoplasm

chromatin has a clumpy and smudgy appearance

Question 9

what do NK cells look like?

Answer 9

they are larger than unstimulated T and B cells

more abundant cytoplasm

less condensed chromatin pattern

Question 10

what are plasma cells?

Answer 10

specialized B cells that make tons of antibodies

Question 11

what do plasma cells look like?

Answer 11

there’s lots of protein production happening from all the antibodies being made so they have a unique appearance

the nucleus is eccentric (off-center**), pushed to the side by a big glob of pale-staining rough endoplasmic reticulum

clumps of chromatin arranged around periphery of nucleus

Question 12

Where do T cells form and mature?

Answer 12

T cells are formed in the bone marrow and mature in the thymus.

Question 13

what happens when you have an underdeveloped or absent thymus?

Answer 13

results in recurrent viral and fungal infections due to the lack of mature T cells available to fight infections.

like in DiGeroge syndrome

Question 14

how are T cells differentiated from one another?

Answer 14

by the various receptors on their cell surface

Question 15

what do helper T cells do?

Answer 15

also called CD4+ cells

• assist in the activation of macrophages
• help with the maturation of B cells into antibody-secreting plasma cells

Question 16

what do CD8+ Cells do?

Answer 16

cytotoxic T cells

they secrete molecules that help destroy whatever cell they are bound to

Question 17

what do CD25+ T cells do?

Answer 17

help modulate immune responses

Question 18

what are the types of T cells?

Answer 18

helper T cells

CD8+ T cells

CD25+ cells

Question 19

what are T cells implicated in?

Answer 19

type IV hypersensitivity reactions and in acute and chronic organ rejection

Question 20

where do B cells form and mature?

Answer 20

B cells also arise from lymphoid stem cells within the bone marrow – but unlike T cells, B cells stay in the marrow to mature

Question 21

what are the roles of B cells?

Answer 21

they are able to secrete cytokines (signaling molecules)

they can differentiate into plasma cells, which make antibodies

Question 22

what are memory B cells?

Answer 22

upon coming into contact with an antigen for the second time, can mount a swift response to the infection

this is the idea behind vaccines! if we can “prime” the body to recognize an infection by using part of a virus or bacteria, then when we encounter the pathogen our body will be able to quickly and efficiently fight off the infection

Question 23

what is agammaglobulinemia?

Answer 23

not being able to form mature B cells

Question 24

what is multiple myeloma?

Answer 24

creating an overabundance of plasma cells

a malignancy in which plasma cells proliferate in the bone marrow

Question 25

what is x-linked agammaglobulinemia?

Answer 25

not being able to form mature B cells

characterized by a complete lack of immunoglobulin (antibodies) due to the inability of B cells to mature and differentiate into plasma cells

Question 26

B cells can differentiate into which two types of cells?

Answer 26

memory B cells and plasma cells

Question 27

what do NK cells do?

Answer 27

they are pre-programmed to recognize virus-infected cells and tumor cells

destroy target cells via the exocytosis of cytoplasmic granules containing two key enzymes, perforin and granzyme

Question 28

where do NK cells come from?

Answer 28

lymphoid stem cells

just like T cells and B cells

Question 29

what is perforin?

Answer 29

it creates pores, or holes, within an infected cell’s membrane that allow granzymes to pass into the cytoplasm of the infected cell.

it’s inside the cytoplasmic granules of NK cells

Question 30

what are granzymes?

Answer 30

serine proteases that, once inside the infected cell, initiate apoptosis, or programmed cell death. This helps stop the progression of the virus or the tumor

granzymes enter the infected cell after perforin has created pores in the cell membrane

it’s inside the cytoplasmic granules of NK cells

Question 31

what do NK cell deficiencies cause?

Answer 31

rare but lead to increased susceptibility to herpesvirus and papillomavirus infections.

Question 32

Which two enzymes do natural killer cells use to fight virus-infected cells and tumor cells?

Answer 32

NK cells use perforin and granzymes to fight virus-infected cells and tumor cells

Question 33

which cell marker identifies a helper T cell?

Answer 33

CD4

all T cells have the CD3 cell marker

Question 34

which cell marker identifies a a cytotoxic T cell?

Answer 34

CD8

Question 35

which cell marker identifies a regulatory T cell?

Answer 35

CD25

Question 36

which cell marker identifies a NK cell?

Answer 36

CD56