Respuesta Adaptativa Primaria y Secundaria | | UPV

Understanding Primary and Secondary Immune Responses

Overview of Immune Responses

• The learning objective is to understand the differences between innate and adaptive immune responses, specifically primary versus secondary responses. This includes identifying key characteristics that differentiate them.

Antibodies and Their Role

• Upon infection, there is an increase in a specific set of proteins known as immunoglobulins, which are antibodies found in plasma. These proteins help distinguish between primary and secondary immune responses.

Characteristics of Immune Responses

• Primary Response: This is the initial response when encountering an antigen (a pathogen). It typically produces fewer antibodies compared to subsequent encounters.

• Secondary Response: Involves subsequent encounters with the same microorganism, leading to a more robust antibody production due to memory cells formed during the primary response.

Key Differences Between Primary and Secondary Responses

• Antibody Quantity: The amount of antibodies produced during a primary response is significantly lower than in a secondary response.

• Timeframe for Antibody Production: A primary response can take up to two weeks for significant antibody levels, while a secondary response can occur within just over a week after re-exposure to the same pathogen.

Types of Antibodies Produced

• In primary responses, Immunoglobulin M (IgM) is predominantly produced; however, in secondary responses, Immunoglobulin G (IgG) becomes the main type produced along with other classes like IgA depending on environmental cytokines present during activation.

Isotype Switching and Memory Cells

• For different classes of immunoglobulins to be produced beyond IgM, B cells require assistance from T helper cells (Th). This interaction occurs mainly in secondary lymphoid organs such as lymph nodes where Th cells induce gene expression changes necessary for producing IgG or other types instead of IgM.

Importance of Immunological Memory

• The concept of immunological memory plays a crucial role in adaptive immunity; it allows for rapid and effective responses upon re-exposure to pathogens due to clonal expansion of memory cells that persist throughout an individual's life. These memory cells reside primarily in bone marrow and lymphoid tissues.

Understanding Isotype Switching in Immune Responses

The Role of Cytokines and T Cell Collaboration

• Isotype switching is influenced by the collaboration of T cells and the presence of specific cytokines in secondary lymphoid organs.

• Immunological responses are enhanced due to memory and proliferation, leading to quicker and more intense reactions.

• Changes in isotypes also affect effector functions, indicating a dynamic response mechanism within the immune system.

Primary vs. Secondary Immune Responses

• Primary immune responses are characterized exclusively by IgM production, which is less effective against pathogens.

• Secondary immune responses involve isotype switching, allowing for the generation of various immunoglobulins beyond IgM.

• Secondary responses are more efficient as they occur in greater quantities, earlier, and with higher effectiveness against pathogens.