Lymphoid

Enzymatic Action and Immune Responses

• Lysozyme hydrolyzes bacterial cell wall components, leading to cell death.
• Complement plays a crucial role in innate immunity by enhancing opsonization, promoting inflammation, and directly lysing pathogens.

Differences Between Immune Responses

• Adaptive immune responses are characterized by specificity and memory, differentiating them from rapid and nonspecific innate immunity.
• Immediate, nonspecific actions are associated with innate immunity.

Cellular Components and Functions

• Natural killer cells destroy various unhealthy host cells, including tumor and virus-infected cells.
• Toll-like receptors (TLRs) enable leukocytes to recognize pathogen-associated molecular patterns (PAMPs), activating immune responses.
• Phagocytic leukocytes like macrophages and neutrophils remove invaders that breach physical barriers.

Adaptive Immunity Dynamics

• The adaptive immune response is also known as acquired immunity, featuring specific responses to pathogens.
• Helper T cells bind to MHC class II molecules on antigen-presenting cells (APCs) with their TCR, promoting immune responses.

T Cell Functions and Characteristics

• Cytotoxic T lymphocytes (CTLs) specifically kill infected or abnormal cells.
• CTLs utilize CD8 coreceptors to enhance binding to target antigens presented by MHC class I molecules.
• T lymphocytes are MHC restricted, meaning they recognize antigens only if presented by MHC molecules.
• Memory helper T cells persist long-term after an initial immune response, facilitating faster responses to future infections.

Antigen Presentation and Immune Mechanisms

• MHC class II proteins are synthesized in the endoplasmic reticulum and transported to the cell surface for antigen presentation.
• MHC class I molecules present 'self-antigens' to help the immune system differentiate between healthy and unhealthy cells.
• Antigen-presenting cells such as dendritic cells, macrophages, and B cells present antigens to lymphocytes.

Cytokines and Their Roles

• Interferon-γ modulates the activity of certain local cells during inflammation, enhancing immune responses.

B Cells and Antibody Functions

• B lymphocytes mature in bone marrow and further differentiate to produce antibodies.
• The Fc region of antibodies is recognized by cell surface receptors on basophils and mast cells, triggering allergic reactions.
• IgG is a stable, highly soluble antibody capable of crossing the placental barrier, providing fetal immunity.
• IgM is produced primarily during the initial immune response and is effective in activating the complement system.
• IgE, though less abundant, binds to mast cells and basophils, playing a key role in allergic reactions.
• IgD, the least abundant immunoglobulin, serves as an antigen receptor that triggers B-cell activation.

Functions of Antibodies

• Antibodies can specifically bind to and neutralize viruses and toxins, agglutinate bacterial cells, and precipitate soluble antigens, demonstrating diverse protective roles in the immune response.

Test your knowledge about the structure and functions of immunoglobulins, including the design of antibody molecules, the Fc region, and their recognition by cell surface receptors. This quiz covers essential concepts related to immunoglobulins.