3.6 Specific cellular defences against pathogens

Question 1

What are Lymphocytes?

Answer 1

white blood cells
involved in the specific immune response.

Question 2

What do Lymphocytes respond to?

Answer 2

to specific antigens on
invading pathogens.

Question 3

What makes lymphocyte receptors specific to particular antigens?

Answer 3

Lymphocytes have a single type of membrane receptor which is specific for one antigen.

Question 4

What happens when an antigen binds to a lymphocyte receptor?

Answer 4

leads to repeated lymphocyte division, resulting in the formation of a clonal population of identical lymphocytes.

Question 5

What are Antigens?

Answer 5

are molecules, often proteins
located on the surface of cells that trigger a
specific immune response.

Question 6

Name the two types of Lymphocytes

Answer 6

B lymphocyte
T Lymphocyte

Question 7

What do B lymphodytes do?

Answer 7

B lymphocytes produce antibodies against
antigens and this leads to the destruction of
the pathogen.

Question 8

What are Antibodies?

Answer 8

Y-shaped proteins that have
receptor binding sites specific to a particular
antigen on a pathogen.

Question 9

How do Antibodies work?

Answer 9

Antibodies become bound to antigens, inactivating the pathogen. The resulting antigen-antibody complex can
then be destroyed by phagocytosis.

Question 10

What causes an allergic reaction in the immune system?

Answer 10

B lymphocytes can respond to antigens on
substances that are harmless to the body. This hypersensitive response is called an allergic reaction

Question 11

What do T lymphocytes do?

Answer 11

T lymphocytes destroy infected body cells by
recognising antigens of the pathogen on the
cell membrane and inducing apoptosis.

Question 12

What is Apoptosis

Answer 12

T lymphocytes attach onto infected cells and
release proteins. These proteins diffuse into
the infected cells causing production of selfdestructive enzymes which cause cell death.
The remains of the cell are then removed by
phagocytosis.

Question 13

How can autoimmune diseases develop from T lymphocyte activity?

Answer 13

T lymphocytes can normally distinguish
between self-antigens on the body’s own
cells and non-self-antigens on infected cells.
Failure of the regulation of the immune
system leads to T lymphocytes responding to
self-antigens. This causes autoimmune
diseases.

Question 14

What happens during a secondary response?

Answer 14

• these memory cells rapidly give rise
  to a new clone of specific lymphocytes.
  These destroy the invading pathogens before
  the individual shows symptoms.
• antibody production is greater and more rapid than
  during the primary response.

Question 15

What does HIV do?

Answer 15

causes depletion of T lymphocytes which
leads to the development of AIDS