Immunopathology

 Immunopathology: An Overview

Immunopathology is the study of how the immune system causes disease. Our immune system is designed to protect us from foreign invaders, such as bacteria and viruses, but sometimes it can cause harm by attacking our own tissues and organs. Understanding the mechanisms of immunopathology is crucial for developing treatments for a wide range of diseases, from autoimmune disorders to allergies and transplant rejection.

Innate Immunity

Innate immunity is the first line of defense against foreign invaders and is also known as nonspecific immunity. This type of immunity is present at birth and does not change over time. It is characterized by a rapid and nonspecific response to a wide range of pathogens, such as bacteria and viruses. Some of the key components of innate immunity include:

Physical and chemical barriers: The skin and mucous membranes provide physical barriers that prevent pathogens from entering the body. Chemicals, such as lysozyme in tears and saliva, also help to kill pathogens.

• Inflammatory response: Inflammation is a crucial component of the innate immune response, helping to destroy pathogens and prevent their spread.
• Phagocytosis: Phagocytes, such as macrophages and neutrophils, are cells that can engulf and destroy pathogens.

Characteristics of Innate Immunity

Rapid response: The innate immune response is rapid and can occur within minutes of pathogen exposure.

Nonspecific: Innate immunity does not target specific pathogens, but instead provides a broad and nonspecific response to a wide range of pathogens.

Limited memory: Unlike the adaptive immune system, innate immunity does not have memory and does not provide long-lasting protection against a specific pathogen.

Adaptive Immune System

The adaptive immune system, also known as specific immunity, is the second line of defense against foreign invaders. It is characterized by a slow but specific response to specific pathogens. This type of immunity is acquired over time through exposure to antigens, such as bacteria and viruses. Some of the key components of the adaptive immune system include:

• T lymphocytes (T cells): T cells are responsible for cell-mediated immunity and help to destroy infected cells directly.
• B lymphocytes (B cells): B cells produce antibodies, which are proteins that target specific antigens and help to neutralize or destroy them.

Acquired (Specific) Immunity

Acquired immunity is the immunity that is gained over time through exposure to antigens, such as bacteria and viruses. This type of immunity provides long-lasting protection against specific pathogens and is the result of the adaptive immune response. There are two types of acquired immunity:

Humoral Immunity

Humoral immunity is the type of immunity that is mediated by antibodies, which are produced by B cells. Antibodies target specific antigens and help to neutralize or destroy them. Humoral immunity is effective against extracellular pathogens, such as bacteria and viruses, that are present outside of cells.

Cellular Immunity

Cellular immunity is the type of immunity that is mediated by T cells, which help to destroy infected cells directly. Cellular immunity is effective against intracellular pathogens, such as viruses, that are present inside cells.

Major Histocompatibility Complex MHC

The Major Histocompatibility Complex (MHC) is a group of genes that play a critical role in the immune system's ability to recognize and respond to foreign invaders, such as bacteria and viruses. The MHC is located on chromosome 6 and is divided into two classes, MHC class I and MHC class II.

Overall, the MHC is a crucial component of the immune system and plays a critical role in our ability to recognize and respond to foreign invaders. Understanding the function and mechanisms of the MHC is essential for the development of treatments for a wide range of diseases, from autoimmune disorders to transplant rejection.

Types Major Histocompatibility Complex MHC

There are two main types of Major Histocompatibility Complex (MHC) molecules: MHC class I and MHC class II.

1. MHC class I molecules are expressed on the surface of nearly all nucleated cells in the body and present antigens from within the cell to CD8+ T cells. This allows T cells to recognize and respond to pathogens that have entered and infected the cell.
2. MHC class II molecules are expressed primarily on immune cells such as dendritic cells, macrophages, and B cells. These molecules present antigens from outside the cell to CD4+ T cells, allowing T cells to recognize and respond to extracellular pathogens.

In addition to these two main classes, there is also a third type of MHC molecule, MHC class III, which is involved in a variety of functions, including the regulation of the immune response and the complement system.