Linfócitos, antígenos e anticorpos

Summary

In this lecture, Professor Luiz Amarante discusses key elements of adaptive immunity, including lymphocytes, antigens, and antibodies. He explains the origin and maturation of lymphocytes, the role of T and B cells, and the immune response they initiate. The video covers the distinction between antigenicity and immunogenicity, and elaborates on immunoglobulins, their structure, and their role in immune responses. Emphasis is placed on the interaction between antibodies and antigens, the importance of different immunoglobulin classes, and their contribution to immunity, including local and systemic defense, allergic responses, and antigen recognition.

Takeaways

• 😀 Lymphocytes are white blood cells originating from hematopoietic stem cells in the bone marrow, and they play a crucial role in adaptive immunity.
• 😀 There are two main types of lymphocytes: T lymphocytes (T cells) and B lymphocytes (B cells), which develop from lymphoid precursors in the bone marrow.
• 😀 T lymphocytes mature in the thymus, while B lymphocytes mature in the liver during fetal development, and they can be differentiated through surface markers.
• 😀 T lymphocytes are classified into three types: helper T cells, cytotoxic T cells, and regulatory T cells, each with specific immune functions.
• 😀 B lymphocytes are responsible for producing antibodies and are heavily reliant on T helper cells and antigen-presenting cells to mount an immune response.
• 😀 Antigens are foreign molecules that can trigger an immune response, with epitopes being the specific regions of antigens recognized by immune cells.
• 😀 Antigens must be foreign to the body, with a molecular weight above 5000 daltons to be recognized, and they can include parts of pathogens or synthetic molecules.
• 😀 Immunogenicity is the ability of an antigen to trigger an immune response, while antigenicity refers to the ability of a molecule to be recognized as foreign by the immune system.
• 😀 Immunoglobulins (antibodies) are gamma globulins produced by B lymphocytes, with specific binding sites for antigens. They play a central role in immune responses.
• 😀 Immunoglobulins are divided into five classes (IgM, IgG, IgA, IgE, IgD), each with distinct roles, such as immune activation, pathogen neutralization, and allergy mediation.

Q & A

What are lymphocytes and what is their role in the immune system?

Lymphocytes are round, mononuclear cells found in peripheral blood. They play a crucial role in adaptive immunity, being involved in the recognition of pathogens and initiating immune responses. They include T cells, B cells, and Natural Killer (NK) cells.

How do lymphocytes originate and differentiate?

Lymphocytes originate from pluripotent hematopoietic stem cells in the bone marrow. They differentiate into T lymphocytes, B lymphocytes, and Natural Killer (NK) cells. The process involves the precursor lymphoid lineage, with further maturation occurring in specific organs like the thymus for T cells and fetal liver for B cells.

What is the significance of the hemogram in diagnosing infections?

A hemogram is a valuable diagnostic tool that helps assess the presence of infections, whether viral or bacterial, and can provide insights into conditions like anemia. It measures the relative and absolute counts of various blood cells, including lymphocytes, which comprise about 40% of white blood cells.

What are antigens and how do they trigger immune responses?

Antigens are molecules that are recognized as foreign by the immune system, triggering an immune response. They typically come from pathogens and contain specific regions, known as epitopes, which are detected by T or B lymphocytes and antibodies.

What is the difference between antigenicity and immunogenicity?

Antigenicity refers to the ability of a molecule to be recognized as foreign by the immune system, while immunogenicity refers to the ability of that molecule to induce an immune response. All immunogenic molecules are antigenic, but not all antigenic molecules are immunogenic.

What are immunoglobulins, and how do they function in immunity?

Immunoglobulins (Ig), also known as antibodies, are gamma globulins produced by B lymphocytes. They are key players in humoral immunity, binding to specific antigens to neutralize pathogens and trigger other immune mechanisms like complement activation.

What are the different classes of immunoglobulins?

Immunoglobulins are classified into five main types: IgM, IgG, IgA, IgE, and IgD. Each has distinct functions, with IgM being the first produced during immune responses, IgG providing long-lasting immunity, IgA protecting mucosal surfaces, IgE playing a role in allergic reactions, and IgD being involved in the activation of B cells.

How do B lymphocytes produce antibodies?

B lymphocytes initially produce IgM antibodies upon activation. When stimulated by helper T cells, they undergo class switching, enabling the production of other antibody classes like IgG and IgA, which are specific to the antigen encountered.

What is the role of T helper cells in the immune response?

T helper cells play a vital role in orchestrating the immune response. They activate B cells to produce antibodies, assist cytotoxic T cells in killing infected or cancerous cells, and regulate other immune cells to ensure a balanced response.

How do immunoglobulins contribute to pathogen neutralization?

Immunoglobulins contribute to pathogen neutralization by binding to pathogens, preventing them from infecting host cells. They can also activate the complement system, opsonize pathogens to enhance phagocytosis, and facilitate cell-mediated cytotoxicity.