Johnston Sr. High Forensics Mrs. Florio Forensic Serology Johnston Sr. High Forensics Mrs. Florio

Learning Objectives 1) List the A-B-O antigens and antibodies found in the blood for each of the 4 different blood types – A, B, AB, O 2) Understand and describe how whole blood is typed 3) List and describe forensic tests used to characterize a stain as blood

Learning Objectives (continued) 4) Understand the concept of antigen/antibody interactions and how it is applied to species identification and drug identification 5) Understand the inheritance of blood types

History Karl Landsteiner – figured out blood was categorized – won Noble Prize All human blood is not the same Blood transfusions were previously a failure before this time Developed ABO system How may blood help at a crime scene?

The Nature of Blood Mixture of cells, enzymes, proteins, and inorganic substances Fluid portion – plasma Mostly water, 55% of blood content Suspended in plasma – cells (45%) Red blood cells (erythrocytes) White blood cells (leukocytes) Platelets Yellow portion in pic is serum (shown when Clotting factor in blood is removed, centrifuged)

Antigens Role of RBCs? Transport oxygen to body tissues and remove carbon dioxide from tissues On surface of all RBCs there are millions of chemical structures called ANTIGENS a substance, usually a protein, that stimulates the body to produce antibodies against it

How does this relate to blood type? Blood Type A – each RBC has A antigens on surface Blood Type B – RBCs have B antigens Blood Type AB – RBCs have both A and B antigens Blood Type O – RBCs don’t have either A or B antigen

What about the Rh factor? + or -? Rh factor – another antigen, sometimes called the D antigen If you have it on RBCs = + If you lack it = - In blood banks, they must look for the presence of A, B, and Rh factor before donating blood

Antibodies Serum contains proteins called antibodies Protein in the serum that destroys or inactivates a specific antigen Anti-A – specific for only A antigen Anti-B - for only B antigen Anti-D – for only D antigen Antiserum – blood serum containing specific antibodies

Antigen-Antibody relationship Antibody reacts only with its specific antigen Serum with anti-B added to RBC carrying B antigen, two will combine, causing antibody to attach itself to cell Antibodies are bivalent – have 2 reactive sites, can attach to 2 RBCs

Agglutination Antibody’s ability to be bivalent creates vast network of cross-linked cells seen as clumping, or agglutination. Normal blood (L) antigens & antibodies coexist b/c antibodies present are not specific towards any of antigens A foreign serum was added to blood (R) and causes antigen/antibody reaction, causing RBCs to link (agglutinate)

Blood Groups

Blood Typing Serology – study of antigen-antibody reactions Ex: ABO identity Type A type is agglutinated by anti-A serum (not natural) Type B aggl. by anti-B Type AB aggl. by both anti-A and anti-B Type O aggli. by neither antibody sera

Population Distribution of Blood Type AB – 3%

Population Frequencies

Cool Website on Blood Typing http://nobelprize.org/educational_games/medicine/landsteiner/readmore.html Blood Typing Game

Level 6 Article Quiz Name one example of a test to detect blood. What are the four different blood types? What are the three main antigens? Where are they found specifically? What do antibodies do to antigens? Name 3 components to blood.

Level 6 continued… 6) What term describes the way blood flows slowly? a) water y b) viscosity c) spatter 7)Which blood type has the highest frequency? (most common, neglecting Rh) 8) A person with blood type B has ____ antigens and ___ antibodies.

Level 6 continued… 9) Blood that flies off a surface under pressure is a(n) __________ stain. a) projected b) transfer c) colloid 10) WBCs make up ___ percent of total blood volume. a) 50% b) 10% c) 5% 11) This is the name for a test used to determine if blood is animal or human.

Level 7 Quiz Which scientist was responsible for organizing blood into types? If you have blood type O, with blood types can you receive? Name the 4 main blood types. What are the three “solid” parts in the blood?

Level 7 continued… 5) Be specific…where are antigens found? 6) Someone with blood type AB has ______ antigens and ____ antibodies. 7) What is the most common blood type? (neglecting Rh) 8) Term describing the ability of antibodies to attach to 2 antigen site.

Forensic Characterization of Bloodstains Questions the criminalist must ask regarding blood stains… 1) Is it blood? 2) From what species does the blood originate? 3) If blood is human, how closely can it be associated with a particular individual?

Types of Tests Presumptive Confirmatory Is It Blood, Semen, Urine, Saliva? Look for proteins, substance activity Confirmatory Confirms the presence of the bodily fluid

COLOR TESTS – Presumptive test for Blood Kastle-Meyer Test Based on the fact that blood hemoglobin possesses peroxidase-like activity Hemoglobin: RBC protein that transports oxygen Peroxidases: enzymes that accelerate the oxidation of many organic compound when combined with peroxides Combination of blood, peroxide, & phenolthalein reagant produces pink color

More on Kastle-Meyer Why is it not confirmatory? False positives – oxidizing metals, potatoes, horseradish

Luminol – Another Presumptive Test for Blood Reaction of luminol with blood produces light, rather than color Must darken room – will produce a faint, blue glow – luminescence Extremely sensitive, capable of detecting bloodstains diluted up to 300,000 times

Luminol – What you see

Takayama – Confirmatory for blood Tests for human hemoglobin Small amount of blood added to microscope slide Chemical solution is added and heated Crystals viewed under microscope Also uses microscopy to detect blood cells

Precipitin Test Human or animal origin? Precipitin – antibody that reacts with its corresponding antigen to form a precipitate when animals are injected with human blood, antibodies form that react with the invading human blood to neutralize its presence

Gel Diffusion Antibodies and antigens will diffuse or move toward one another on a plate made with a gel medium (agar). Can also do this under influence of electrical field (electrophoresis)