Warmup 1 How does the body defend itself

Warm-up 1. How does the body defend itself? 2. How does the body “remember” pathogens? 3. How does the body recognize foreign antigens as different from “self”?

Self vs. Non-self • Body recognizes its own proteins as “self” • Proteins that are not recognized as self act as antigens, and an immune response with antibodies occurs An example: Red blood cells have surface proteins that can act as antigens if they are not recognized by the immune system

Proteins on red blood cells • Two types of proteins can be expressed on the surface of red blood cells: “A” or “B” • These proteins can be expressed in different combinations

Red blood cell expressing “A” protein Red blood cell expressing “B” protein Red blood cell expressing “A” and “B” protein Red blood cell expressing no protein

Protein on Cells Blood type A A B B A and B AB None O

Blood typing and transfusions • If donated blood has a protein that the immune system does not recognize, that protein will act as an antigen, and the body will produce an immune response. • The body will “reject” the blood as foreign, antibodies will be produced against it, and the person will die as a result of the transfusion.

Reject or accept? (case #1) Patient’s blood type = A Donor’s blood type = A Will an immune response (rejection) occur? [THINK: Are any foreign antigens being added? ]

Reject or accept? (case #2) Patient’s blood type = A Donor’s blood type = B Will an immune response (rejection) occur? [THINK: Are any foreign antigens being added? ]

Reject or accept? (case #3) Patient’s blood type = AB Donor’s blood type = A Will an immune response (rejection) occur? [THINK: Are any foreign antigens being added? ]

Reject or accept? (case #4) Patient’s blood type = O Donor’s blood type = B Will an immune response (rejection) occur? [THINK: Are any foreign antigens being added? ]

Blood typing activity YOUR TASK:

Inheritance of Blood Type Three alleles for the blood protein gene exist in the population: A = gene produces “A” protein B = gene produces “B” protein O = gene does not produce a protein Blood type is produced by the combination of two alleles- (one from each parent)

Genetics of Blood Type Phenotype Genotype A AA or AO B BB or BO AB AB O OO

Organ transplants and rejection • Body tissues and organs have many more proteins that can act as antigenssometimes resulting in over 100 “types” of tissue • This makes it very difficult to match an organ donor with a patient whose immune system will not reject it as “foreign”