SerologyChapter 12

Serology

•It is the study of body fluids ▫Blood▫Saliva▫Semen▫Urine

Functions of Blood

•Blood has 3 main functions▫Transportation

Oxygen, carbon dioxide, wastes, nutrients, heat, & hormones

▫Regulation Ph, body temperature, water content

▫Protection From disease & loss of blood

Characteristics of Blood

•Thicker than H2O and flows more slowly•100.4 F temp•Ph of 7.4•8% of body weight•Blood volume

▫Male- 5-6 liters▫Female- 4-5 liters

Components of Blood

•Blood consists of▫55% plasma▫45% cells

99% RBC (red blood cells) <1% WBC (white blood cells) and platelets

Plasma

•90% H2O•7% plasma proteins

▫Albumin- maintain blood osmotic pressure▫Globulin- form antigen- antibody complexes▫Fibrinogen- for clotting

•3% other substances▫Electrolytes, nutrients, hormones, gases,

waste products

Formed Elements of Blood

•Red blood cells (erythrocytes)•White blood cells (leukocytes)•Platelets (thrombocytes)•Serum

Formation of Blood Cells

•Blood cells need to be replaced continuously▫Die within hours, days, or weeks▫Process is called hematopoiesis

•In embryo, occurs in yolk sac, liver, spleen, thymus, lymph nodes, & red bone marrow

•In adult- occurs in red bone marrow of sternum, ribs, skull, & pelvis

Red Blood Cells (RBC)

•Contains hemoglobin (carries oxygen)▫Gives it its red color▫Makes up 1/3 of cell’s weight

•Is biconcave▫Increased sa:vol▫Flexible for narrow passages▫No nucleus or organelles (no cell division)

•In adult▫Male- 5.4 million RBC/gttp (drop)▫Female- 4.8 million RBC/gttp

White Blood Cells (WBC)

•Are leukocytes•Have a nucleus and no hemoglobin•Classified as granular or agranular based

on presence of granules in the cytoplasm▫Granulocytes- neutrophils, eosinophils,

basophils▫Agranulocytes- monocytes, lymphocytes

Platelets

•Disc shaped•No nucleus present•Normal count

▫150000- 400000 gttp/blood•Other blood cell counts

▫5 million RBC▫5-10000 WBC

Serum

•Is the liquid that separates from the blood when a clot is formed

Immunoassay Techniques

•Are available for detecting drugs through antigen-antibody reactions

•2 types of processes▫EMIT (enzyme multiplied immunoassay

technique) Antibodies that bind to a specific drug are

added to a subject’s urine▫RIA (radioimmunoassay)

Uses drugs labeled with radioactive tags

Antigen-Antibody Reactions

•When an animal is injected with an antigen, its body will produce a series of different antibodies, all of which are designed to attack some particular site on the antigen of interest▫Called polyclonal antibodies

•Antibodies designed to combine with a single antigen site can be manufactured▫Called monoclonal antibodies

Forensics of Blood

•The criminalist must be prepared to answer the following questions when examining dried blood▫Is it blood?▫From what species did the blood originate?▫If the blood is of human origin, how closely

can it be associated to a particular individual

•Detection of blood is best made by means of a preliminary color test

Presumptive Tests for Blood Determination•3 tests

▫Kastle-Meyer color test Is a mixture of phenolphthalein and hydrogen

peroxide Hemoglobin of blood will cause a deep pink

color if blood is present▫Hematest tablet

Reacts with the heme group in blood causing a blue-green color

▫Luminol test Reacts with blood to produce light

Human vs. Animal Blood

•Once the stain has been characterized as blood, the precipitin test will determine whether the stain is of human or animal origin▫Uses antisera normally derived from

rabbits that have injected with the blood of a known animal to determine the species origin of a questioned bloodstain

•Once the bloodstain has been determined to be of human origin, the blood is typed

The Discovery of Blood Types

•Before Landsteiner’s discovery, countless people died from blood transfusions▫There was an assumption back then that

everybody had the same blood•In 1900, Landsteiner proved that there

are four different types of blood based on the presence or absence of specific antigens on the surface of RBC’s▫Known as ABO blood group

•In 1940, he discovered the Rh factor

Blood Types

•RBC surfaces are marked by genetically determined glycoproteins & glycolipids▫Agglutinogens or antigens▫Distinguishes at least 24 different blood

types Most common= ABO & RH

ABO Blood Groups•Based on 2 glycolipid antigens (A & B)

found on the surfaces of RBC▫Antigen A only= type A blood▫Antigen B only= type B blood▫Both antigens= type AB blood▫No antigens= type O blood

•Plasma contains antibodies or agglutinins to the A or B antigens not found in your blood▫Anti- A antibody reacts with antigen A▫Anti-B antibody reacts with antigen B

Breakdown of ABO Blood Types

•Type A- 42% •Type B- 12%•Type AB- 3%•Type O- 43%

Rh Factor

•Antigen was discovered in rhesus monkey▫Called Rh antigen or D antigen

•People with Rh agglutogens on RBC surface are Rh+ (normal plasma contains no anti-Rh antibodies)

•Antibodies develop only in Rh- blood type & only with exposure to the antigen

Breakdown of Rh Blood Type

•Rh+- 85%•Rh- - 15%

•Of the Rh+ population, 85% are Caucasians, 94% are African Americans, and 99% are Asians

Universal Donors and Recipients•People with type AB blood are called

universal recipients▫No antibodies present▫Can receive blood from anybody

•People with type O blood are called universal donors▫No antigens present▫Can donate blood to anybody

Typing and Cross Matching of Blood• Mixing of incompatible blood causes

agglutination (visible clumping)▫Formation of antigen- antibody complex that

sticks cells together▫Not the same as blood clotting

• Typing involves testing blood with known antisera that contains antibodies A, B, or Rh+

• Cross matching is to test by mixing donor cells with recipient’s serum

• Screening is to test recipient’s serum against known RBC’s having known antigens

ABO vs. DNA

•Prior to the advent of DNA typing, bloodstains were linked to a source by ABO bloodtyping

•DNA analysis has allowed forensic scientists to associated blood and semen stains to a single individual