Serology only

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Serology

Chapter 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 H

2

100.4 F temp

O and flows more slowly

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% H

2

O

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 bluegreen 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

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