Question

Each group of questions consists of five lettered headings followed by a list of numbered phrases or sentences. For each numbered phrase or sentence, select the one heading that is the most closely related to it and fill in the corresponding oval on the answer sheet. Each heading may be used once, more than once, or not at all in each group. Questions \(3-6\) refer to the following: (A) Diaphragm (B) Rib cage (C) Alveoli (D) Bronchioles (E) Trachea Tiny air ducts covered by cilia and mucus.

Short answer

The correct answer is (B) Complement proteins which have a nonspecific action in the immune system.

Step-by-step solution

Understand the Role of Complement Proteins

Complement proteins are a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism. They are non-specific meaning they will attack any foreign cells, not just a specific type of cell.

Compare with other immune system components

While some immune cells (like lymph nodes, MHC markers, Interferon) have more targeted responses, Complement proteins work to assist or 'complement' these targeted responses with a broad, nonspecific action against all foreign cells that enter the organism.

Key concepts

Complement Proteins

Complement proteins are vital components of the immune system, known for their ability to enhance the effectiveness of antibodies and phagocytic cells. They operate by marking pathogens for destruction and facilitating the process by which immune cells clear them from the body. However, one of the unique features of complement proteins is their non-specific action. This means they do not target a specific pathogen; instead, they will respond to any foreign cell or pathogen that invades the body. This broad approach helps in the initial defense against infections, providing an immediate response to a wide range of pathogens.

A typical action of complement proteins involves forming a complex known as the membrane attack complex (MAC). This complex can puncture the cell membrane of invaders, leading to their destruction. This rapid response is crucial in the early stages of an infection, holding the line while the more specific aspects of the immune system, like antibodies, prepare to respond. By boosting other immune functions in this way, complement proteins bridge innate and adaptive immunity.

Non-specific Immune Response

The non-specific immune response, also known as the innate immune response, acts as the first line of defense against pathogens. Unlike the adaptive immune system, which generates a targeted response against specific pathogens, the non-specific immune response is always ready to act, providing immediate defense against a wide range of organisms. This means that it doesn’t require the pathogen to be recognized or remembered—as in the case of a specific immune response—to act.

Key components of this system include physical barriers such as the skin and mucous membranes, as well as internal defenses like phagocytic cells, inflammation, and, notably, complement proteins. These components work together to prevent pathogens from causing disease and help eliminate them before they can multiply. Inflammation, for example, involves his/her own response molecules and cells, resulting in increased blood flow and white blood cells to the site of infection, which helps to quickly contain infections.

• Skin acts as a physical barrier.
• Phagocytes "eat" invading pathogens.
• Inflammatory responses allow more immune cells to reach affected areas.

Immune Cells

Immune cells are the protectors of the body, constantly on the lookout for invading pathogens and foreign substances. They play essential roles in both the innate (non-specific) and adaptive (specific) immune responses. Each type of immune cell has unique functions and mechanisms by which they protect the body.

Phagocytic cells such as macrophages and neutrophils are part of the non-specific immune system and are often the first responders to microbial threats. They engulf and digest pathogens, presenting them to the relevant parts of the immune system for further action. Other cells, like lymphocytes, including T-cells and B-cells, belong to the specific immune system and target distinct antigens present on pathogens. This targeted response provides a memory of the pathogen, ensuring faster and more efficient responses upon subsequent exposures.

• Macrophages and Neutrophils: Engulf and destroy pathogens.
• T-Cells: Target specific pathogens and help regulate immune responses.
• B-Cells: Produce antibodies that specifically bind to antigens.

Understanding the diverse roles of immune cells helps in comprehending how our bodies mount effective defenses against diseases, with each cell type contributing uniquely to maintaining health.