Lab Exam 2

antigen (protein from a bacteria or virus)

• has diff sites that will evoke an immune response

• immune response results in the production of antibodies that bind to antigen specifically

• sites on antigen is called an epitope

• specific interaction btwn antibodies and antigens can be used in many ways in the design of diagnostic tests. major types of immune-based diagnostic tests that are used are agglutination tests and ELISA tests

  • when antigen and antibodies are mixed, each antibody can bind two antigens = antibody-antigen complex, immune complex, or the clumps that can be seen = agglutination

serum

• fluid that remains after blood coagulates, coagulation removes all the clotting proteins, RBC, platelets, and WBC

• serology: testing of serum specimens from patients to determine if antibodies against a particular antigen are present

  • antibodies indicated the patient has been exposed to the pathogen or has been vaccinated against the pathogen

  • antibodies carried against a particular antigen means a person has a titer

• titers above a particular dilution indicate an immune status that would provide protection from infection by the pathogen: protective immunity

• if titer increases after several weeks, the infection was still ongoing at time of 1st blood draw

mono-latex slide test

• determines if a patient has antibodies to Epstein-Barr virus (EBV), the pathogen that’s responsible for mononucleosis

hemagglutination

• involves RBCs and is used in blood typing:

  • specific interaction btwn antibodies against the various antigens on the surface of RBCs

  • blood typing is accomplished by mixing blood droplets with a solution of antibodies against type A protein and a solution of antibodies against B protein, respectively

Normally, persons will have a certain amount of antibody against the ABO antigens that they do not carry. The reasons for the presence of this antibody have never been discerned. If the wrong type of blood is given to a patient, the antibodies in their serum will bind to and cause the destruction of these newly introduced RBCs in the transfusion. When these RBCs are destroyed, chemicals are released that increase vasodilation and vascular permeability. This results in rapid loss of fluids into the tissues on a systemic basis and a systemic loss of vascular tone. Together, these two changes in the blood vessels will send the patient into shock. Use of the rapid blood typing reaction can eliminate blood type mismatches.

ELISA tests

• ELISA= enzyme linked immunosorbent assay

  • used to detect the presence of antibodies in a patient’s serum against a particular antigen and this is exemplified by HIV test.

  • also used in clinical samples and is the basis of rapid Strep test

• These tests rely upon an antibody that has been covalently attached to an enzyme (horseradish peroxidase or alkaline phosphatase are the two most common enzymes used). This enzyme-antibody combination is referred to as the conjugate or secondary antibody. All ELISA tests also rely upon a chromagen (enzyme substrate). The chromagen is a substrate for the enzymes listed above, when acted upon by these enzymes, the chromagen will change color. A color change indicates presence of the enzyme and thus, the presence of the antibody to which it is linked.

trophozoite stage

• the active feeding stage for protozoan parasites

• most of these organisms reproduce by simple cell fission while others are able to participate in a rudimentary form of sexual reproduction

• Trophozoites lack the protective

  covering of the cysts and are destroyed in the stomach after ingestion causing no illness. As the

  disease resolves, normal rates of bowel movement return, and there is time for the encysted stage

  of the organisms to develop.

• Those protozoans that are acquired orally will pass through a stage known as the cyst; this stage of the organism’s life cycle is able to withstand severe environmental conditions, even stomach acid.

Entamoeba histolytica

This organism causes a condition known as amebiasis in humans. Ingestion of water or food contaminated with feces leads to the introduction of the cyst stage. Four free-swimming amoebas emerge from the cyst in the small intestine. They colonize the cecum (first part of the large intestine) and usually cause a mild condition typified by diarrhea and intestinal discomfort.

More serious cases involve bloody stools (dysentery), inflammation of the appendix and

perforation of the bowel. The organism can spread to other abdominal organs such as the spleen

or liver. It can penetrate the diaphragm leading to infection of the lungs.

Giardia intestinalis

causes a condition called giardiasis typified by diarrhea, cramps, flatulence and muscle weakness. Stools will often contain much unabsorbed fat. The protozoan is maintained in the environment because animals can also be infected.

Trichomonas vaginalis

trichomoniasis is a common sexually transmitted diseases. Trichomoniasis is caused by the organism Trichomonas vaginalis. Infection of the female usually involves the mucosa of the vagina, vulva and cervix. Symptoms of the infection in the female are vaginal itching, irritation, and a significant yellow-green, foul-smelling discharge 5 to 28 days after exposure. Lesions may be present on the vaginal mucosa. Infection of the male usually involves the urethra, prostate and seminal vesicles. Infection of the urethra can lead to pain when urinating (dysuria).

Diagnosis involves a vaginal or urethra swab and subsequent microscopic observation of the organism in a smear made from the swab. The trophozoite stage is pear-shaped with four flagella and an undulating membrane. This protozoan does not form cysts.

Plasmodium species

• malaria

  • It is responsible for

    millions of deaths annually. The etiologic agent of this disease is one of several species of the

    genus Plasmodium. This agent is transmitted by the bite of certain types of mosquito.

• The bite of an Anopheles mosquito, results in the injection of mosquito saliva containing

  sporozoites into the bloodstream of a human. The sporozoite moves through the bloodstream

  until they take up residence within cells of the liver. Within liver cells, the sporozoites undergo

  division and form many cells referred to as merozoites. Rupture of the infected liver cells leads

  to the release of thousands of merozoites into the bloodstream.

• A portion of the merozoites in the red

  blood cells will develop into male and female gametocytes. Red blood cells containing the

  gametocytes are ingested when another mosquito bites an infected human for a blood meal. The

  gametocytes are freed from the red blood cells in the intestine of the mosquito and bond together

  to form a zygote. The zygote ultimately differentiates into a cyst. Sporozoites are released from

  the cysts which then migrate to the salivary glands of the mosquito.

hosts

• Organisms that host the development stages of the parasite are referred to as intermediate hosts. The organism that hosts the sexually mature stage of the parasite is referred to as the definitive host.

• Flukes and tapeworms belong to the phyla Platyhelminthes and are commonly referred to as the

  flatworms. These organisms have a complex life cycle, usually infecting different hosts at

  different stages of their development.

Schistosoma mansoni

this organism is also referred to as a blood fluke. These organisms cause the disease

schistosomiasis. Initially, the entry of the schistosome through the skin causes dermatitis with a

pruritic papular (itchy and bumpy) rash. The acute phase of schistosomiasis, a condition referred

to as Katayama fever, may occur 2 to 4 weeks after heavy exposure.