文档介绍：国外动物学35-资料
The Immune System
An animal must defend itself from the many dangerous pathogens it may encounter in tefense by attacking microbes directly or by impeding their reproduction.
Antimicrobial Proteins
About 30 proteins make up the complement system, which can cause lysis of invading cells and help trigger inflammation.
Interferons provide innate defense against viruses and help activate macrophages.
Inflammatory Response
In local inflammation, histamine and other chemicals released from injured cells promote changes in blood vessels that allow more fluid, more phagocytes, and antimicrobial proteins to enter the tissues.
Natural Killer Cells
Natural killer (NK) cells patrol the body and attack virus-infected body cells and cancer cells.
Trigger apoptosis (programmed cell death) in the cells they attack.
Acquired Immunity
Acquired immunity is the body’s second major kind of defense.
Involves the activity of lymphocytes.
Acquired Immunity
An antigen is any foreign molecule that is specifically recognized by lymphocytes and elicits a response from them.
A lymphocyte actually recognizes and binds to just a small, accessible portion of the antigen called an epitope.
Antigen Recognition by Lymphocytes
The vertebrate body is populated by two main types of lymphocytes which circulate through the blood:
B lymphocytes (B cells)
T lymphocytes (T cells)
B Cell Receptors for Antigens
B cell receptors bind to specific, intact antigens.
Y-shaped: two identical heavy chains & two identical light chains.
Variable regions at the tip provide diversity.
T Cell Receptors for Antigens and the Role of the MHC
Each T cell receptor consists of two different polypeptide chains.
The variable regions form the antigen binding site and provide a diversity of T cells.
V
V
C
C
T Cell Receptors for Antigens and the Role of the MHC
T cells bind to small fragments of antigens that are bound to normal cell-surface proteins called