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BIO 102 Lab 04, The Immune System and Blood Cellstrnn
GENERAL BIOLOGY II (BIO 102)
Northern Virginia Community College
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BIO 102 Lab 04: The Immune System and Blood Cells
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If you have a disability that makes it difficult to complete this lab, please contact your instructor. Please provide your instructor a copy of the Memorandum of Accommodation (MOA) from NVCC Disability Support Services.
OBJECTIVES:
Become familiar with the different types of blood cells and their functions Understand antigen-antibody binding and its importance in transplants Learn about the effects of vaccination on a population and the protection gained from herd im- munity
INTRODUCTION Our immune system functions to keep us safe by destroying and removing things that can make us sick. This system is not composed of individual organs, but several structures in our body work as part of the immune system to produce, house, or circulate immune components, including the bone marrow, spleen, and lymphatic vessels (Figure 4). The immune system is composed of physical, chemical, and cellular parts that work together to destroy foreign particles that enter our bodies. Foreign particles can include dangerous pathogens (e., bacteria, viruses, parasites, fungi), toxins, benign molecules such as pet dander or pollen, and even beneficial bacteria or fungi. One part of our immune system, the innate system we are born with fully intact and it naturally produces components to fight things we might face in our everyday lives. The second part of our immune system, the adaptive system, we generate through lifetime exposure and we produce specialized components that are trained during our development and growth.
Innate Immunity The innate immune system—called that because you and everyone around you is born with it—acts in a non-specific way against foreign particles, meaning this “pre-made” innate immune system will attack particles in the same way regardless of the nature of a particle (i., virus vs grass pollen). This system makes no memory about previous encounters or whether its defense to a previous invader was effec- tive or ineffective. The nonspecific immune system's primary function is to prevent us from getting sick from common potentially harmful things in our everyday environment. Major structures of the innate system include our skin, mucus membranes, ear wax, stomach acid, sweat, tears, vaginal secretions, all which help prevent or block entry of harmful particles. If harmful particle is able to enter our bodies, then cells of the innate system called leukocytes or white blood cells (WBCs) can destroy it or can pro- duce antimicrobial proteins that destroy the invaders. Leukocytes can be distinguished from erythro- cytes (red blood cells) that function in oxygen distribution and platelets that function in clotting and tis- sue repair because they are larger, have a clear cytoplasm (thus white blood cell), and they have large
nuclei with distinctive shapes that stain purple when dyed for microscopy. Leukocytes that function in innate immunity, include macrophages, dendritic cells, neutrophils, basophils, eosinophils , and each of these cells has a specific phenotype (characteristic look) as well as particular functions (Table 4).
The innate immune system is powerful and is fundamental to keeping us safe during everyday encoun- ters. Sometimes the response from the innate immune system—and all its physical, chemical, and cel- lular components—is insufficient to fight of a pathogen, such as a virus. This stimulates the second (more targeted) portion of our immune system; the adaptive immune system.
Adapted Immunity The adaptive immune system—called that because the components are “adapted” to the environment each individual has experienced—acts in a unique way against every foreign particle your body encounters during its lifetime. Our adaptive immune system specializes in clearing (destroying) viruses and other particles that our innate immune system is not able to clear. This is because the cells of our adaptive immune system, called T cells and B cells ( Table 4 ) , are made in the presence of the invading particle and therefore are specific to that particle; it is a very targeted attack. However, because the body has to build a defense from scratch, so to speak, the initial formation of an immune
anaphylactic shock and even die. This is because your T cell and B cell response is so massive after subsequent exposure that they can damage your organs, and your body shuts down. However, we can use the memory response to our benefit by stimulating an immune response to deadly pathogens before we actually encounter them. This is called immunization.
Immunity and vaccination Immunization refers to the formation of memory to specific pathogens. This occurs through direct exposure and survival or through vaccination. Vaccines work when the antigenic portions of a pathogen, or the inactivated pathogen (with its antigenic portion intact), are used to stimulate a primary immune response. The vaccination will stimulate an adaptive immune response and build memory without actually causing disease, which could be deadly. After vaccination, if you are ever exposed to the real pathogen in the future, you will now have circulating memory T cells and B cells that can respond and control the pathogen immediately. The length of memory you get depends on the type of pathogen you get infected with, the quantity of antibodies you create, and the type of antibody that is made in the response. For example, vaccinations against the Clostridium tetani bacteria, which causes tetanus, builds immunity for about 10 years. After that time, the memory B cells have mostly died off and disappeared, and so you need a booster shot about every 10 years to prevent infections. But antibodies against the measles virus remain in circulation in your body for the rest of your life, so you only need to be vaccinated once.
When the majority of the population is immunized (either through exposure or vaccines), the high level of immunization in the population becomes a barrier to disease transmission. This is because some pathogens such as viruses require infecting individuals for survival, but if most people are immunized, a virus may not find enough hosts to keep the infection going, and the virus will die off. Immunization is protective for the few individuals in a population that are susceptible to an infection due to immune deficiencies or other ailments. This is referred to as herd immunity. Just as a wild herd of animals protect their weakest by moving them towards the inside of the heard (and away from danger), immunization protects susceptible individuals from infection by “hiding” them away from transmission possibilities.
Medical and scientific use of immune components
Blood cell counts The proportion of different blood cells in blood (Figure 4) can be indicative of various dis- eased conditions and so medical professionals will often do blood cell counts to detect abnor- malities. Blood levels that are too high or too low may indicate health problems. For exam- ple, specific leukocytes will replicate in re- sponse to infections, disease, or injury. High WBC counts with neutrophils could indicate in- fections with bacteria or other pathogens. Sometimes, the immune system will recognize benign substances, such as pollen, dirt, or pet dander, as foreign and dangerous. These sub- stances will stimulate an immune response from basophils, eosinophils, and other immune components. That is the cause of allergic reactions. Sometimes an individuals' immune components can recognize molecules on self-tissues as foreign or dangerous and will attack those tissues. This is how autoimmune diseases such as asthma or diabetes
can arise. Low WBC counts may also indicate disease. For example, autoimmune disorders such as leukemia (cancer of the blood and bone marrow) can result in WBC loss as the cancer destroys blood cells. Infectious pathogens such the Human Immunodeficiency Virus (HIV) specifically targets certain WBCs as hosts for replication. The virus then destroys the host cell as it leaves and once WBC counts drop below 200 cells/mm 3 in blood, an infected person is diagnosed with AIDS (acquired immune defi- ciency syndrome). This means that they have so few white blood cells present in their blood that they are no longer able to fight off any pathogens, even very mild ones.
ELISA (enzyme-linked immunosorbent assay) The ELISA (enzyme-linked immunosorbent assay) can be used to detect the presence of antibodies in solution (as well as proteins, or other molecules). This is because antibodies will only bind to their specific antigen, and so you can test for the presence of specific antibodies if their corresponding antigen is present in a solution. If the antigen is not present, no binding will occur. There are several variations of ELISAs, but two of the most commonly used are direct ELISA and indirect ELISA. In a direct ELISA, antibodies that are conjugated (bound) to an enzyme reporter molecule are used to detect antigen (Figure 2). Indirect ELISA is similar to direct ELISA, but it requires a second and different type of antibody to anchor antigen molecules to the bottom of the test well. In both types of ELISA, the enzyme reporter molecule functions when a substrate (a molecule that the enzyme works on) is added to the solution that has antigen-conjugated antibody binding. The enzyme reaction causes a noticeable color change (Figure 2, step 4). This will only happen if the enzyme-conjugated antibody has been able to bind its antigen. The deeper the intensity of the color change, the more antigen-antibody interactions occurred. No color change indicates no antigen-antibody interaction. The procedure is completed on a small plastic plate that has many wells so numerous samples, at different dilutions, can be run simultaneously.
ELISAs are used by medical professionals to test for the presence of antibodies in serum (fluid portion of blood) that were generated by infections from certain pathogens (adaptive immunity). For example, you might hear in the news that many clinics are currently running antibody testing to see what
2. Analyze the following pictures of blood samples from two different patients, Patient A and Pa- tient B. Use information in the introduction to answer the questions below. Assume these slides are representative of the rest of the blood in the patient.
a. Is blood sample A normal/healthy? Explain why or why not and hypothesize on the health status of Patient A. What might be the cause for any abnormalities (be sure to name any leukocytes present).
. Patient A looks as though they are not in a healthy condition. The leukocytes present are the
lymphocyte, neutrophil, and monocyte. There for , i believe there is an infection or maybe
inflammation in the body.
b. Is blood sample B normal/healthy? Explain why or why not and hypothesize on the health status of Patient B. What might be the cause for any abnormalities.
Patient B looks healthy and/or normal. There is no evidence of leukocytes present and I do not see
any cause for abnormalities, looks to be functioning properly and with no negative reaction.
ACTIVITY B: ELISA assay for detecting the presence of antigen
3. Measles is caused by a virus that is easily transmitted between individuals through the air and it is highly contagious. After a small gathering of 9 people, the host began showing symptoms consistent with measles infection, and then tested positive for the virus. At the hospital, medical personnel wanted to test everyone that attended the party to determine who had been infected with the virus and had generated an immune response (remember ELISAs test for the presence of antibodies against specific antigen). By using an ELISA test, measles infections can be confirmed despite the absence of symptoms (after people have cleared the virus).
a. In your own words, briefly explain how the antibody-antigen portion of the ELISA technique works.
The ELISA technique is used to find substances such any peptides or proteins in the body
b. What causes changes of color in the wells?
The color changes when a chemical reaction occurs with the antibodies of the enzymes.
c. What does a color change from a sample indicate for the individual?
The color change indicates that the antibodies are positive for the thing that it is trying to get rid of.
Below are the color results from an ELISA completed on the 8 party guests. Please note the following: The first and second rows are the positive (+) and (-) controls for the test. The reporter enzyme turned the solution blue in the presence of corresponding antigen- antibody binding. The serum samples from each individual were diluted up to 5 times (2-fold each time) to get an idea of antibody concentration (how much antibody is present in the original sample). The undiluted row would have the highest concentration of antibodies for each individual. As such, the higher the dilution, the lower the concentration of antibody present in the well. These results can be further processed using a device (photometer) that can read specific color intensity, but you will only be doing interpretation of initial pos/neg results.
any difference?
They did not develop the same level of response, because everyone’s genes are different from each
other, their antibodies will react in a different way from others.
g. What do these results indicate for individuals whose serum tested positive at the 1:32 dilution?
This would mean that the blood of the guest is still showing antibodies and that they are still present.
h. If you had to guess, which individuals would have best protection against a subsequent infection with measles virus later in their life?
individual 5 I think would most likely have the best protection.
i. In your own words, explain what might be the importance of doing ELISA tests for SARS-CoV-2?
The ELISA test would help us in finding certain viruses even though individuals may not be
experiencing any symptoms. This would further allow the doctor to help diagnose any further issues
and problems,
ACTIVITY C: Understanding Immunity
3. For this activity you will use information from a simulation of measles transmission to understand spread and herd immunity of the current coronavirus pandemic. Follow the link from the University of Pittsburgh Measles simulator (fred.publichealth.pitt/measles) to observe the difference in disease spread through a school-aged population where 80% of the individuals have been immunized with measles vaccine vs. a population where 95% of the individuals are immunized with measles vaccine. After the activity, answer the questions that follow.
Step 1: For “Select a state”, choose District of Columbia.
Step 2: For “select a city” choose Washington DC.
Step 3: Let the simulation run completely.
a. Take and attach a screenshot of the simulation after 238 days and explain what caused the difference in cases between 80% immunization and 95% immunization in the population of children in Washington D.
b. In your own words, what is herd immunity?
Herd immunity is the resistance to an infectious disease that is based on already pre-existing
immunity because of previous infection or vaccination. Therefore, the virus cannot get back to the
host.
c. Scientists believe that about 70% of the population would have to be immunized with SARS-
BIO 102 Lab 04, The Immune System and Blood Cellstrnn
Course: GENERAL BIOLOGY II (BIO 102)
University: Northern Virginia Community College
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