Summary IB Biology Topic 11: Animal Physiology

IB TOPIC 11 | ANIMAL PHYSIOLOGY
2016 | SYJ0014


Topic 11.1: Animal physiology – Antibody production and vaccination
Immunity is based on recognition of self and destruction of foreign material.

• Understanding: Every organism has unique molecules on the surface of its cells.

 Antigens: molecules recognized as foreign by the immune system
 Antibodies: globular proteins that recognize and act against a specific antigen

 Major Histocompatibility Complex (MHC): set of cell surface proteins essential for the acquired
immune system to recognize foreign molecules and oneself
 Unique nature of MHC: every individual expresses different MHC
 Recognizing foreign material: MHC is used by the immune system to recognize its
own or foreign material
 Problem with MHC: MHC is responsible for the rejection of tissue/organ transplant

 MHC recognition and rejection mechanism:
 NK cell management: NK cells kills cells that do not express own MHC
 T cell and B cell management: T and B cells only react with antigens
that are presented by own MHC

• Understanding: Pathogens can be species-specific although others can cross species barriers.

 Pathogens: diseases causing organism
 Species specific: able to infect a certain type of organism
 Species general: are able to cross the species barrier

 Zoonosis: name given to a pathogen that can cross the species barriers
 Factors affecting zoonosis: growth of contact between animals and human through livestock and disruption of habitat

• Understanding: B lymphocytes are activated by T lymphocytes in mammals.

 T helper cells: plays a role in the production of antibodies by B cells and activation of cytotoxic cells
 B helper cells: produces specific antibodies as a part of specific immunity

 T-helper cell activation:
 Phagocyte enter lymph node: macrophage/dendritic cells travel to lymph
node once engulfed antigen
 Phagocyte antigen presentation: macrophage/dendritic cells present antigen
on cell surface
 T cell activation: T cell recognize the antigen presented by APC (antigen
presenting cells) via protein complex MHC
 Helper T cell activation: CD4+ T cells are activated as they bind
to MHC class II
 Cytotoxic T cell activation: CD8+ T cells are activated as they
bind to MHC class I

 Humoral immune response:
 B cell encounters antigens: B cell encounters antigen produced by pathogens
 B cell activation: activated T helper cells which recognizes the same antigen
binds to the MHC II on the surface of the B cell to stimulate maturation
 Clonal selection: rapid replication of B cells occurs and they differentiate into
plasma and memory cells
 Plasma cell: cell that produce antibodies
 Memory cell: cell that stores information to prepare for future
invasions
 Plasma cell activity: plasma cell (with plentiful ER) produces antibodies that
are released to circulate our body
 Antibody activity: antibody circulates our body and binds to free pathogen for
indirect/direct destruction

• Understanding: Activated B cells multiply to form clones of plasma cells and memory cells.

 B plasma cells: cells that indirectly kills pathogen through secretion of antibodies through a humoral immune response
 B memory cells: cells that remain long after the infection and remain inactive unless the same pathogen infects the body again

• Understanding: Plasma cells secrete antibodies.

 Clonal selection: generation of large number of plasma cells that generate one specific antibody type

• Understanding: Antibodies aid the destruction of pathogens.

 Antibodies: molecules that aid the destruction of pathogens




LAST EDITED 2017-03-17 | 1