Clase 34 Fisiología Sanguínea - Inmunidad (Linfocitos T y B) (IG:@doctor.paiva)

In-depth Exploration of Blood Physiology and Immunity

In this class, the focus is on blood physiology and immunity. Key topics include generalities of immunity, acquired immunity, types of lymphocytes, antibodies, complement system activation, and antigen recognition.

Generalities of Immunity

• The immune system comprises innate and acquired immunity.

• Innate immunity is nonspecific and present from birth.

• Components include phagocytosis by leukocytes, skin resistance to microorganisms, and chemical compounds in the blood that destroy pathogens.

Acquired Immunity

• Acquired immunity is specific and potent against pathogens.

• It develops through antibody formation and lymphocyte activation.

• Two types: humoral (B lymphocytes) and cellular (T lymphocytes).

Antigen Recognition

• Antigens initiate acquired immunity.

• Antigens must have a molecular mass >8,000 and epitopes for immune recognition.

• Lymphocytes play a crucial role in recognizing antigens.

Lymphocyte Development and Specificity

This section delves into the development of lymphocytes in various tissues like bone marrow, thymus, liver during fetal life. It emphasizes the specificity of T cells towards antigens.

Lymphocyte Origin

• Lymphocytes originate mainly in lymphoid tissues like bone marrow.

• T cells are processed in the thymus while B cells undergo processing in the liver during fetal life.

T Cell Specificity

• T cells develop specificity towards numerous antigens.

• Sensitized T cells recognize specific antigens upon re-exposure for targeted destruction.

Thymic Selection Process

• The thymus ensures self-tolerance by eliminating autoreactive T cells.

• By exposing preprocessed T cells to self-antigens, it eliminates those reacting to self-tissues.

B Cell Development and Antibody Production

This part focuses on B cell development contrasting with T cell reactivity. It highlights antibody diversity generated by B cells for effective immune responses.

B Cell Functionality

• B cells primarily produce antibodies rather than directly targeting antigens like T cells do.

Desarrollo del Sistema Inmunológico

This section discusses the development of the immune system, focusing on lymphocytes, antigens, and antibody production.

Lymphocyte Specificity and Clonal Selection

• Lymphocytes have specificity towards antigens, with each lymphocyte capable of producing a single type of T lymphocyte or antibody.

• Lymphocytes differentiate into clones specific to particular antigens. B lymphocytes form clones specific to an antigen stimulating them.

Specificity in Immune Response

• T lymphocytes have specific markers on their membrane that react only with corresponding antigens.

• Antigen sensitization occurs when an antigen matches surface receptors on lymphocytes, leading to a specific immune response.

Activación de Linfocitos y Macrófagos

This part explores the role of macrophages in activating lymphocytes and the subsequent immune response.

Macrophage Function in Immune Activation

• Macrophages phagocytize microorganisms releasing antigenic products that activate lymphocytes through direct contact.

• Macrophages present antigenic products to lymphocytes, leading to the activation of specific clones for future defense against the same microorganism.

Colaboración entre Linfocitos T y B en la Respuesta Inmunitaria

The collaboration between T and B lymphocytes is crucial for an effective immune response.

Helper T Cells and Antibody Production

• Helper T cells secrete substances called cytokines that activate specific B lymphocytes to produce antibodies.

• Memory T cells remain dormant until reactivated by exposure to a specific antigen, resulting in a more potent secondary antibody response.

Formación de Anticuerpos por Linfocitos B

Details the process of antibody formation by B lymphocytes upon encountering foreign antigens.

Antibody Production Process

• Upon encountering an antigen, B cells differentiate into plasma cells that secrete antibodies at a rapid rate.

Understanding Antibodies and the Complement System

In this section, the discussion revolves around antibodies, specifically immunoglobulins, their structure, types, functions, and interactions with antigens. Additionally, the role of the complement system in enhancing immune responses is explored.

Antibodies: Structure and Types

• Immunoglobulins constitute 20% of all plasma proteins and are composed of two light and two heavy polypeptide chains.

• There are five types of antibodies (IgM, IgG, IgA, IgE, IgD) with distinct functions.

• Antibodies can act against invaders through direct action or by activating the complement system.

Complement System Functionality

• The complement system consists of around 20 proteins that enhance immune responses.

• Antigen-antibody binding activates the complement cascade leading to various defense mechanisms like opsonization and lysis.

Memory Cells and Immune Response

• Memory cells such as memory T lymphocytes play a crucial role in mounting faster and stronger immune responses upon re-exposure to antigens.

• Specific proteins on antigen-presenting cells determine whether an antigen will be presented to T lymphocytes for immune response activation.

Lymphocytes and Immune Response

In this section, the speaker discusses the different types of lymphocytes, focusing on T lymphocytes and their roles in the immune response.

Types of Lymphocytes

• Helper T cells are crucial in stimulating the growth and differentiation of other immune cells.

• Interleukins such as IL-2, IL-3, IL-4, IL-5, and IL-6 play significant roles in immune responses.

• Helper T cells are targeted by HIV, leading to compromised immune function.

Role of Cytotoxic T Cells

This part delves into cytotoxic T cells' functions in directly attacking pathogens and infected cells.

Functions of Cytotoxic T Cells

• Cytotoxic T cells perform direct attacks on microorganisms and infected cells.

• They release perforin to create pores in target cell membranes for cytotoxic substances.

Suppression by Regulatory T Cells

The discussion shifts to regulatory T cells that help prevent excessive immune reactions.

Regulatory T Cell Functions

• Regulatory T cells suppress the activities of cytotoxic and helper T cells to prevent self-damage.