Immune and Lymphatic System for the DAT
/Learn key DAT concepts related to innate and adaptive immunity, anatomy of the immune system, antigens, and antibodies, plus practice questions and answers
Everything you need to know regarding the immune and lymphatic systems for the dat
Table of Contents
Part 1: Introduction to the immune system
Part 2: Innate vs adaptive immunity
Part 3: Innate immune system
a) Anatomical barriers
b) Cellular component
c) Complement system
d) Cytokines
e) Inflammation
Part 4: Adaptive immune system
a) B cells and humoral immunity
b) T cells and cytotoxic immunity
Part 5: Anatomy of the immune system
a) Bone marrow
b) Spleen
c) Thymus
d) Lymphatic system
Part 6: Antigens and antibodies
a) Antibody structure
b) Antigen presentation
c) Recognition of self and non-self
Part 7: High-yield terms
Part 8: Questions and answers
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Part 1: Introduction to the immune system
The immune system serves as the body's defense mechanism against foreign invaders and diseases. It's a highly intricate system that relies on continuous feedback to develop immunity. Our discussion will primarily revolve around two major immune system components: innate and adaptive immunity. Additionally, we'll explore other bodily elements that contribute to immune responses and delve into how the immune system's components combat diseases.
To gain a comprehensive understanding of the immune system in preparation for the DAT, it's essential to first understand the immune system's components and their functions. Subsequently, familiarizing yourself with key principles likely to show up on the exam is crucial. Throughout your study, drawing visual flow charts illustrating the interplay of these components can also help.
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Part 2: Innate vs adaptive immunity
The highest level of classification within the immune system distinguishes between the innate immune response and the adaptive immune response. We will delve deeper into these aspects in the upcoming sections. In essence, the innate immune response consists of bodily components that non-discriminately combat diseases and foreign pathogens, whereas the adaptive immune response is more selective in its targeting of specific diseases. Your innate immune response is inherent and at the ready from birth, capable of rapidly responding to foreign pathogens within seconds to hours. In contrast, the adaptive immune response operates on a considerably longer timescale, spanning several days.
These broad classifications can be further dissected into their individual components, a subject that we'll explore in greater detail in subsequent sections (parts 3 and 4).
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Part 3: Innate immune system
As previously noted, the innate immune system plays a crucial role in general disease protection but lacks the capacity to identify specific foreign agents or diseases. This innate immune system can be subdivided into two primary components: the non-cellular segment and the cellular segment. The non-cellular component encompasses physical barriers within the body, along with signaling molecules. On the other hand, the cellular component comprises diverse types of white blood cells. These elements within the innate immune system can act independently to combat pathogens, or they can collaborate in a coordinated response referred to as inflammation.
a) Anatomical barriers
The foremost physical barrier shielding the body against pathogens is the skin—a tightly packed layer of cells that acts as a formidable defense, effectively blocking external materials from infiltrating the body and substantially reducing the risk of disease. Beyond its role as a physical shield, the skin contributes to the innate immune response through its remarkable capabilities, such as sweating and the periodic shedding of the top skin layer, which assists in shedding any potential pathogens.
Additionally, the skin enhances the adaptive immune response by housing specific cellular components poised to manage any pathogens that may breach its protective layer. While the skin stands as a prominent external barrier, other anatomical defenses within the body, including the mouth and nose, serve as potential entry points for pathogens.
For instance, the gastrointestinal tract plays a pivotal role in the innate immune response, as it's susceptible to bacteria and pathogens that can enter through the mouth. The first line of defense here is found in saliva, containing the enzyme lysozyme, which effectively breaks down bacterial cell walls.
Moreover, the highly acidic environment of the stomach significantly contributes to immune response. The stomach's low pH, around 2, renders it a hostile environment for most microorganisms, ensuring that only a limited number can survive. Furthermore, various components of the gastrointestinal tract collaborate to deter disease. Peristalsis, for example, propels food through the digestive tract, thus preventing pathogens from accumulating in the body.
Remarkably, the naturally occurring gut flora in the gastrointestinal tract plays a crucial role in preventing bacterial infections. These beneficial bacteria act as a counterbalance to pathogenic bacteria by outcompeting them and constraining their uncontrolled proliferation.
In the respiratory system, innate immunity is further fortified as it effectively filters out pathogens and microparticles present in the air. Similar to saliva's function, the mucus within the respiratory tract contains lysozyme to combat bacteria. It also serves as a trap, intercepting particles and preventing their unhindered entry into the lungs. Mucus works with cilia in the respiratory tract to propel microbes toward the pharynx, where they can be swallowed and subsequently destroyed within the acidic environment of the stomach.
b) Cellular component
The cellular component of the innate immune response consists of white blood cells, also known as leukocytes. These white blood cells exhibit diverse functions, with some contributing to the innate immune response, while others play a role in the adaptive response. This section provides an introduction to various types of leukocytes and describes their classifications.
1. Neutrophils: These are the most abundant white blood cells and specialize in phagocytosing bacteria. Neutrophils are often regarded as the initial responders to infections, making an elevated neutrophil count indicative of an ongoing infection.
2. Lymphocytes: Lymphocytes are the second most prevalent type of white blood cell. However, it's crucial to note that not all lymphocytes are involved in the innate immune response. There are three principal types: B cells, T cells, and natural killer cells. B and T cells primarily contribute to the adaptive immune response, a topic we'll explore in the subsequent section. On the other hand, natural killer cells target infected cells, specifically those afflicted by viruses and tumors. They serve as a somewhat specialized facet of the innate immune response as they home in on cells marked for destruction.
3. Monocytes: Following neutrophils and lymphocytes, monocytes are the next most abundant white blood cells. They migrate to tissues throughout the body where they differentiate into dendritic cells or macrophages. Dendritic cells hold a pivotal role as intermediaries between the adaptive and innate immune responses by presenting antigens to T cells, a subject we'll delve into later. Macrophages function as substantial cellular "garbage processors" within the body, efficiently phagocytosing numerous pathogens and foreign particles.
4. Eosinophils: Eosinophils are a specialized type of white blood cell that primarily targets parasitic infections.
5. Basophils: Although they constitute a smaller segment of white blood cells, basophils are vital for allergic responses, chiefly through the release of histamine and heparin during inflammatory reactions.
6. Mast Cells: Similar to basophils, mast cells are found predominantly in mucous membranes and connective tissues. These cells share a role in allergic responses.
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