Practice Test

πŸ“ Explanation:

After 48 hours of inflammation, the predominant cells are typically monocytes, which differentiate into macrophages.

1. Neutrophils: Neutrophils are the most abundant type of white blood cells and are the first to arrive at the site of inflammation. They are the primary cells that dominate the early stages of acute inflammation, which typically occurs within the first few hours (around 4-6 hours) after the onset of injury or infection. Their main function is to phagocytose (engulf and destroy) microbes and release enzymes and proteins that help to break down and dissolve damaged tissue. Although they play a crucial role in the early stages, their numbers tend to decrease after this initial phase, making them less likely to be the predominant cells after 48 hours.

2. Monocytes: Monocytes are the largest of the white blood cells and are part of the mononuclear phagocytic system. They are recruited from the bloodstream to the site of inflammation in response to chemical signals called chemokines. After approximately 24-48 hours of inflammation, monocytes start to predominate the scene. These cells differentiate into macrophages once they have infiltrated the tissue. Macrophages are the "clean-up crew" of the immune system, engaging in phagocytosis, antigen presentation, and the release of cytokines that help coordinate the overall inflammatory response. They are crucial for the later stages of inflammation, which include the removal of debris, repair, and resolution.

3. Eosinophils: Eosinophils are white blood cells that are involved in the immune response to parasitic infections and in the pathogenesis of certain allergic diseases. They are not typically the predominant cells in the general inflammatory response and are more commonly associated with allergic inflammation and parasitic infections. After 48 hours, eosinophils are less likely to be the main cell type unless the inflammation is of an allergic or parasitic nature, in which case they might be present in larger numbers. However, in a typical non-specific inflammatory process, they are not the predominant cell type after this duration.

4. Lymphocytes: Lymphocytes are a type of white blood cell that is essential for the adaptive immune response. There are two main types: T-lymphocytes and B-lymphocytes. While they are involved in the later stages of inflammation, particularly in the adaptive immune response, they are not typically the predominant cells after 48 hours in a general acute inflammatory setting. Lymphocytes are more likely to be found in higher numbers during the later stages of inflammation, particularly during the resolution phase or in chronic inflammation, when the body is mounting a more specific response to the invading pathogen.

πŸ“ Explanation:

Opsonins are molecules that enhance the phagocytosis of antigens by binding to their surfaces and acting as markers or labels that make them more recognizable to phagocytes.
1. lgG (Fc fragment): Immunoglobulin G (IgG) is the most common antibody isotype in human serum. It plays a crucial role in the secondary immune response. The Fc region of IgG is the fragment that interacts with Fc receptors present on the membrane of phagocytic cells. When an antigen is coated with IgG, the Fc fragments of these antibodies can bind to the Fc receptors, leading to the activation of the phagocytic process. This is known as antibody-dependent phagocytosis, where the antibody acts as an opsonin to facilitate the recognition and engulfment of the antigen by phagocytic cells.

2. C3b of complement cascade: The complement system is a cascade of proteins that can be activated in response to an infection or the presence of foreign substances. C3 is a central protein in this system, and when it is cleaved into C3a and C3b, the latter can bind directly to antigens. C3b acts as an opsonin by coating the surface of pathogens. The presence of C3b on a microbial surface allows it to be recognized by complement receptors on phagocytic cells, such as macrophages. This interaction enhances the efficiency of phagocytosis, as the receptors can recognize the bound C3b and engulf the antigen more readily.

3. IgM (Fc fragment) and C5b of complement cascade: While IgM is the first antibody isotype produced in response to an infection and can also opsonize antigens, it is less efficient than IgG due to its pentameric structure and lower affinity for phagocytic receptors. However, it is not as commonly associated with phagocytosis as IgG. Regarding C5b, it is part of the membrane attack complex (MAC) and is involved in the direct destruction of pathogens rather than acting as a classical opsonin that leads to phagocytosis. The MAC assembles on the surface of the antigen and creates pores, leading to osmotic lysis and destruction of the cell membrane.

πŸ“ Explanation:

The correct answer is: 1. Progression ¨ vascularization ¨ invasion ¨ detachment ¨ embolization.

Explanation of the stages for a malignant tumor cell:

1. Progression: This is the initial stage of tumor development where the cells acquire the ability to proliferate in an uncontrolled manner. This can be due to genetic mutations that alter the normal regulatory mechanisms that control cell division. The tumor grows locally within the tissue or organ of origin.

2. Vascularization: Also known as angiogenesis, this stage involves the formation of new blood vessels that supply the tumor with nutrients and oxygen, which is essential for its continued growth and progression. The tumor cells secrete factors that stimulate the growth of blood vessels into the tumor mass.

3. Invasion: The malignant tumor cells develop the capability to invade surrounding tissues. They secrete enzymes that degrade the extracellular matrix and basement membrane, allowing them to move through these barriers and invade neighboring tissues and organs.

4. Detachment: During this stage, tumor cells detach from the primary tumor site. This is facilitated by the loss of cell-to-cell adhesion molecules and the degradation of the extracellular matrix by proteolytic enzymes.

5. Embolization: Detached tumor cells can then enter the lymphatic system or bloodstream. This process is known as intravasation. They travel through these vessels as emboli and can potentially form new tumors at distant sites, which is the process of metastasis.