The Importance of Comprehending the Human Bodys Lines of Defense - Assignment Example

387: Learning Psychology My concept: Human body’s nonspecific second line of defense Unit 5 Marked Project Introduction College biology is a difficult and demanding course with many students struggling to grasp the basic concepts. However, it is important that the students master them early to avoid difficulties in later semesters when the courses become more advanced and challenging. Grades can then suffer as students struggle with the early concepts and have to keep going back to them, thereby hampering their advance learning (Glucksman, 2006). One such topic is “immunity” which is a fundamental concept in biological sciences, immunology and medicinal studies. In order to master these subjects, the student must have strong understanding of this topic. Immunity is further subdivided into a number of concepts to facilitate the learning for students. 1. First line of defense 2. Second line of defense: a) Non-Specific Phagocytic cells Neutrophils, macrophages, eosinophil and dendritic cells Antimicrobial proteins Inflammatory response Natural killer cells b) Specific The concept chosen here to demonstrate the learning method is human body’s nonspecific second line of defense. This is aimed towards college students and it has been assumed that they have prior understanding of the components of the defense mechanism and know the structure of proteins and WBCs (Glucksman, 2006). In Part 1, a brief description of the concept along with critical features will be provided. All variables properties that misapprehended as critical features of the concept will be underlined. In Part 2, using examples and non-examples the concept will be explained in an east-to-grasp manner for students. These examples and non-examples have been chosen to make the concept easier for the students and will be analyzed further to allow students to distinguish between the relevant and irrelevant details based on their relation with critical features to gain clarity of concept. Part 3 will finish the learning exercise with a set of questions aimed at testing the comprehension of the project by the student. They will be different than the examples and non-examples so as to gauge student’s learning. For each short question, the student should be able to give a brief explanation and identify the critical feature involved. Answers have been provided in the Appendix for reference of both students and teachers. Part 1: Concept Description Human body’s second line of defense system protects the body against all types of nonspecific infections and antigens. All the features work together to provide the body with the immunity enabling it to survive and fight the foreign invasions. The critical features are: 1. Non specificity 2. Second line of defense These two critical features have further subdivisions: Phagocytic cells Antimicrobial proteins Inflammatory response Natural killer cells Each critical feature will be further explained in detail. Their function, site of action, and effectiveness in combating the disease will be discussed with the students. Also, the results if second line of defense is compromised will be highlighted. It is aimed that all the relevant information about the concept is covered in the exercise making students fully equipped to handle further courses/topics in biology. Type 1: Phagocytic cells are involved in the nonspecific immunity as they attack and ingest the foreign particles, antigens. There are a few types of phagocytic cells involved in this mechanism i.e. neutrophil, eosinophil, macrophages and natural killer cells (Glucksman, 2006). Example: Eosinophil is a type of phagocytic cell that is involved in combating infections and multicellular parasites. They make up 1-6% of the WBCs. Eosinophils develop and mature in bone marrow. They are found in the medulla and the junction between the cortex and medulla of the thymus, and, in the lower gastrointestinal tract, ovary, uterus, spleen, and lymph nodes, but not in the lung, skin, oesophagus, under normal conditions. The presence of eosinophils in these latter organs is associated with disease. Eosinophils persist in the circulation for 8–12 hours, and can survive in tissue for an additional 8–12 days in the absence of stimulation. They circulate in blood and migrate to inflammatory sites in tissues and are activated by Type 2 cytokines released from a specific subset of helper T cells.They release chemicals to neutralize the antigens or destroy them through oxidation (Glucksman, 2006). Eosinophils along with basophils and mast cells, are important mediators of allergic responses and asthma pathogenesis and are associated with disease severity.  Type 2: Antimicrobial proteins are released by virus-infected cells and are involved in inhibiting infection of neighboring cells. They are linked to killing microorganisms nonspecifically (Mescher, 2009). Example: Interferon. Vast knowledge of this particular particle is unknown however, it is believed to play important role in innate and broad spectrum defense system of the body. Type 3: Inflammation is the sign of infection in any part of the body most probably damage of the tissue. It is a multistep process which is a result of the invasion of a strong antigen. Chemical signals of injury are released by damaged cells, these include histamines & prostaglandins. Signals increase permeability of local capillaries thereby allowing the passage of phagocytes and clotting components to the injured area. Phagocytes then consume any invading pathogens and foreign materials which may have entered the wound. After engulfing, the phagocytes die at the site of injury and cause inflammation (Glucksman, 2006). Type 4: Natural killer cells are a type of cytotoxic cells that specialize in destroying virus infected, worn, or defective cells by lysing them. They are distinct from Natural Killer T cells. NK cells play a major role in the rejection of tumors and cells infected by viruses. They kill cells by releasing small cytoplasmic granules of proteins called perforin and granzyme that cause the target cell to die by apoptosis (programmed cell death).NK cells are activated in response to interferon or macrophage-derived cytokines. They serve to contain viral infections. Patients deficient in NK cells prove to be highly susceptible to early phases of herpes virus infection. The distinction between apoptosis and cell lysis is important in immunology: lysing a virus-infected cell would only release the virions, whereas apoptosis leads to destruction of the virus inside (Mescher, 2009). Part 2: Teachings Example and Non‐Examples In this part of the exercise examples and non-examples will be used to further explain the concept. Since the concept is of higher level, definition of the concept and its features alone is not enough for full comprehension. Therefore, this methodology will reinforce what has been taught earlier. Examples will include the two main critical features described at the start while the non-examples will be missing one of them. Students will be able to distinguish other defense systems of the body from the “nonspecific second line of defense.” Each example and non-example is followed by a question, answer and analysis explaining why it is an accurate example or qualifies as a non-example. Since the concept is highly correlated to the topic of immunity that partial understanding can lead to confusion. Therefore, the teacher will aim to introduce the candidates to other basic aspects of defense mechanism through non-examples. It should be noted that understanding of this part is crucial in mastering the concept because the test that precedes it will follow the same pattern. The level of difficulty will also be similar. Example 1: Neutrophils are involved in body’s second line of nonspecific immunity. Question: What are neutrophils? Are they nonspecific in their function? Answer: Neutrophils are phagocytic cells whose function is to ingest microorganisms and foreign particles. They are nonspecific in their function,and are the predominant cells in pus, accounting for its whitish/yellowish appearance. Neutrophils are recruited to the site of injury within minutes following trauma and are the hallmark of acute inflammation. They are the most abundant among white blood cells. Analysis: This is an example because it contains both the critical features of the concept i.e. non-specificity and second line of defense. In this particular case neutrophils are phagocytic cells which are nonspecific and provide innate immunity to the individual. They play vital role in combatting infection by ingesting and first in aiding against inflammation. Example 2: Skin serves as a nonspecific mechanism of defense. Question: How is skin involved in immunity? Answer: Skin prevents the entry of any antigens into the body. It protects the body against all sorts of bacteria and viruses. It is slightly acidic tough layer of keratin that is impermeable to microbes. In addition the sweat keeps it moist while melanin protects from U.V. It is nonspecific in its function and does not contain any receptors. Analysis: This is a non-example since it does not contain the second critical feature. Skin is involved in the primary defense of the human body not secondary. However, it is non-specific and fulfills criteria 1. Example 3: The time for immune response varies with specific and nonspecific. Question: Which is quicker? Specific immunity or nonspecific? Answer: Nonspecific immune repose is quicker in nature because it does not involve the long process of antigen recognition and production of antibodies that is involved in the specific immune response i.e. cell mediated or humoral. The antigen presenting cell may take a while to manufacture while antibody production can take even weeks. Nonspecific occurs almost immediately (Mills, 2006). Analysis: This is an example to highlight the different aspects of the immunity. It is to equip the students for further learning. Example 4: A wound has been covered with a blood clot. Question: What kind of defense is the clot providing? Answer: The clot is similar to the skin; it is a barrier in the entry of bacteria and other infecting agents. Therefore, it is the nonspecific first line of defense. This barrier is very weak and is a result of the mesh of dead blood corpuscles in the insoluble fibrin strings. Analysis: This is a non example as it contains critical feature 1 but not 2. Example 5: Antibodies. Question: What are antibodies? Answer: Antibodies are specific proteins that have complimentary receptors to the antigens and combat the pathogens by agglutination making them easy to engulf for phagocytes, combine with toxins neutralizing them, immobilize them by attaching with the flagella and punch holes in them destroying their osmotic potential. They are produced by the plasma cells in humoral response which is specific second line of defense (Ross and Pawlina, 2010). Analysis: This is a non example as antibodies are part of send line of defense but specific. Example 6: Question: What is cell mediated response? Answer: It is the one on one combat between T cytotoxic cells and the host cell in which pathogen is hiding. These cells recognize the cells in which foreign particle is hidden, punch hole in them using the enzyme perforin and destroys their osmotic potential. The host cell is finished. This is the second line of defense but specific (Ross and Pawlina, 2010). Analysis: This is a non example as it is the part of specific second line of defense. It fulfills criteria 2 but not 1. Example 7: Active and acquired immunity are involved in second line of defense. Question: What is acquired immunity? Answer: Acquired immunity is different than innate immunity which you are born with. Acquired immunity is built during the whole life through environment or vaccinations etc. These are the following types of acquired immunity: 1. Active Natural Immunity – through natural exposure to an antigen. 2. Active Artificial Immunity – antigen is deliberately introduced to stimulate the immune system. This process is vaccination, and the introduced antigen is the vaccine. The vaccine is either part of the microbe, dead microorganisms, or an altered microorganism. 3. Passive Natural Immunity – transfer of antibodies from a mother to child across the placenta before birth. IgG provides protection for the first few months. IgA can also be passed to the newborn through colostrums and milk. 4. Passive Artificial Immunity – by vaccinating an animal, antibodies and T cells are removed from animal and injected into the individual requiring immunity. It is temporary immunity involved in treatment of rabies, hepatitis, measles, bacterial toxins such as tetanus, diphtheria, botulism, and venoms from poisonous snakes and spiders (Ross and Pawlina, 2010). Analysis: This is a non example as it is the part of specific second line of defense. It fulfills criteria 2 but not 1. Part 3: Test The test below has 10 questions designed to test the comprehension of the concept by the student. They are different from the above examples and non-examples yet follow the same pattern. The student is required to give a short answer and also provide a reason to why he/she thinks it is related to body’s second line of defense. The student is not required to list the critical features involved. If the teaching program is successful the student should be able to show 90% command of the concept. The answers are provided in the Appendix for cross checking. Question 1: Are Natural Killer cells same as the Natural killer T cytotoxic cells? Question 2: Are lachrymal secretions also involved in defense? How? Are they specific or not? Question 3: Why is humoral immune response characterized as second line of defense? Question 4: What is the role of macrophages in immunity? Question 5: What is the key feature that differentiates specific and non-specific immunity? Question 6: Antimicrobial proteins can work in specific defense mechanism as well. Is it true? Question 7: How can we categorize inflammatory response as nonspecific? Question 8: In which category would you place mucous: specific or nonspecific? Question 9: Which immunity would be more effective: specific or nonspecific? Question 10: What will happen if nonspecific second line of defense is compromised? Appendix: Answer Key Question 1: Are Natural Killer cells same as the Natural killer T cytotoxic cells? Answer: No natural killer cells are different from NK T cytotoxic cells. The former are nonspecific while the latter are specific in function. Basic function is however, the same, as both are involved in the one to one killing of cells through oxidation. The T cells are involved in the cell mediated immune response which is the specific second line of defense (Ross and Pawlina, 2010). Analysis: The cytotoxic cells work using specific complimentary receptors present on the antigens and the NK cells. Question 2: Are lacrimal secretions also involved in defense? How? Are they specific or not? Answer: Lacrimal secretions contain mucous, lipids and lysozymes that promote the control of infectious agents and keep the eyes from drying. They arenonspecific in nature as antigens are not recognized and acted upon (Ross and Pawlina, 2010). Analysis: The lacrimal secretion or tears are however, involved in first line of defense and not second, though both share nonspecific mode of action. Question 3: Why is humoral immune response characterized as second line of defense? Answer: Humoral immune response involves the production of antibodies through plasma cells which specific in their function and combine with the antigens to destroy them using different methods i.e. agglutination, neutralization, oxidation etc. It is characterizes as second line of defense as it involves the cells within the body that act against the foreign particles. The primary defense acts from outside the body and involves chemicals and not cells (Ross and Pawlina, 2010). Analysis: The humoral immune response is specific in nature though it is included in the secondary defense mechanism. Question 4: What is the role of macrophages in immunity? Answer: Macrophages are phagocytic cells that are involved in ingesting the foreign particles and cell debris. The process of phagocytosis occurs as the macrophage first engulfs the pathogen, then the lysosomes present in it combine with it to digest/neutralize it. They are also involved in adaptive immunity (Ross and Pawlina, 2010). Analysis: Macrophages involved in phagocytosis are nonspecific and perform secondary defense mechanism. Question 5: What is the key feature that differentiates specific and non-specific immunity? Answer: The key feature that differentiates between specific and nonspecific immunity is the mode of action of the agents involved. In the nonspecific first line of defense the chemical are involved which neutralize any pathogens they encounter. In second line of defense the phagocytes, antimicrobial proteins, and natural killer cells kill/neutralize/ingest the pathogens without recognizing them. As long as they pose a threat to the body, they are eliminated. However, in the specific line of defense, the cells produce highly specific antibodies or kill the pathogens by recognizing them through specific receptors present on their membranes (Mills, 2006). Analysis: The student should have clear understanding of how both types of immunity works so that they have better understanding of the concepts. Question 6: Antimicrobial proteins can work in specific defense mechanism as well. Is it true? Answer: Yes it is true that antimicrobial proteins are involved in specific immunity as well. They are involved in modulating the responses of dendritic cells and cells of the adaptive immune response hence work in specific response as well. Dendritic cells are involved in processing antigen presenting cells, thus making it specific in nature (Mills, 2006). Analysis: Although involved in secondary defense they work both specifically and nonspecifically. Question 7: How can we categorize inflammatory response as nonspecific? Answer: Inflammatory response is nonspecific because it is the after effect of every infection. This is not a specific action that occurs in only some injuries and not in others but in every injury or infection. It is a warning sign that has been the key in diagnosis of many diseases (Mills, 2006). Analysis: This an example of the concept with both critical features involved. Question 8: In which category would you place mucous: specific or nonspecific? Answer: Mucous is the first line of nonspecific defense. It is released from mucous glands and contains proteins mucin and antiseptic agents in aqueous media. It binds with the pathogens nonspecifically and prevents their entry through agglutination. It plays major role in protecting against bacteria, fungi and viruses (Mills, 2006). Analysis: It is a non-example as it contains one of the critical features. It also provides further information needed for full comprehension of the concept. Question 9: Which immunity would be more effective: specific or nonspecific? Answer: Specific immunity is more effective as it involves one to one combat against the foreign particles. It is a highly precise way to kill microbes. Also in specific immunity, memory cells are produced which are involved in secondary immune response, they will be activated if the body comes into contact with the same antigen again and hence this time the disease will not occur but the pathogens will be destroyed before they can do any damage. This response is quicker than the one when pathogen first entered the body (Mills, 2006). Analysis: This question is pertinent to further concepts which should be delivered to the student during the exercise. The students must also learn them. Question 10: What will happen if nonspecific second line of defense is compromised? Answer: If nonspecific second line of defense is compromised the direct effect is on the WBCs (phagocytes). Disease will occur and the more specific second line of defense will be triggered. Antigen presenting cell will be produces and either plasma cells will produce antibodies or T cytotoxic cell will kill the cell (Mills, 2006). Analysis: This question is pertinent to further concepts regarding nonspecific second line of defense which should be delivered to the student during the exercise. The students must also learn them. References Glucksman, MarcJ. Biochemistry and Molecular Biology. Lippincott Williams and Wilkins. 4th Edition. 2006. Print. Mescher, Anthony, L. Junqueira’s Basic Histology: 12th Edition: Text and Atlas. New York: McGraw-Hill Medical. 2009. Print. Mills, Stacey, E. Histology for Pathologists. Lippincott Williams and Wilkins. 3rd Edition. 2006. Print. Ross, Michael, H. and Wojciech Pawlina. Histology: A text and Atlas. Lippincott Williams and Wilkins. 6th Edition. 2010. Print. Read More