Disorders of the Immune System

• Autoimmune Disorders – body produces antibodies against its own tissue, e.g. Grave’s disease (hyperthyroidism) and rheumatoid arthritis

• Allergies occur when the body reacts to materials which should not be antigenic, e.g. peanuts

Immunity

Active immunityProduction of a person’s own

antibodies; long lasting

Passive immunityAn individual is given antibodies by

another ; short-term (weeks- 6 months)

Natural ActiveWhen pathogen

enters body in the normal way, we make antibodies

Natural PassiveFrom mother in

uterus & breast milk

Artificial PassiveImmunoglobulin

injection;extremely fast, but

short lived (e.g. snake venom)

Edward Jenner

Artificial ActiveVaccination – person makes

antibodies without becoming ill

Blood Groups & Immunology

The ABO System

• Discovered in 1901 by Dr. Karl Landsteiner

• 4 main phenotypes (A, B, AB, O)

• Type of inheritence: multiple alleles (each person has only 2 alleles but more than 2 alleles exist)

• Three possible alleles: IA, IB, i

Phenotype vs. Genotype

Phenotype Genotype

A IA IA or IA i

B IB IB or IB i

AB IA IB

O i i

Inheritance of ABO Groups

If the mother has blood type O and her husband is blood type AB, what will be the blood type of their baby?

IA i IA i

IB i IB i

i i

IA

IB50 % chance A blood type

50 % chance B blood type

Distribution of the A allele

Distribution of the B Allele

Distribution of the O Allele

Universal Donor and Recipient

Universal Donor

• Group O

– Carries no A or B antigens

Universal Recipient

• Group AB

– No anti-A or anti-B present

The Rh(D) System

• Discovered in 1940 on Rhesus monkeys

Simple Genetics of Rh(D)

• 86% of caucasians are Rh(D) positive• The d gene is recessive:

– DD & Dd persons are Rh(D) pos– Only dd persons are Rh(D) neg

Distribution of Rh(D) Types

Population Rh(D) pos Rh(D) neg

Caucasian 86% 14%

African-American 95% 5%

Oriental >99% <1%

Significance of Rh(D)

• Rh(D) negative persons exposed to Rh(D) pos blood will develop anti-D

• Anti-D can also be stimulated by pregnancy with an Rh(D) positive baby– Can be prevented by the use of anti-D

immunoglobulin (RhoGam shot) administered before and after childbirth

Inheritance of ABO and Rh(D)

Mother

Group A IA i

Rh(D) pos Dd

Father

Group B IBi

Rh(D) pos Dd

Draw a Punnet Square for this DIHYBRID CROSS; show phenotypic ratios.