TH2 cells activate B cells, inducing a humoral immune response with antibody production against extracellular pathogens and toxins. This immune response also is induced after administration of toxoids and is inactivated or conjugated vaccines.

During the secondary immune response, the immune system can eliminate the antigen, which has been encountered by the individual during the primary invasion, more rapidly and efficiently. Both T and B memory cells contribute to the secondary response.

In a secondary response to the same antigen, memory cells are rapidly activated. This process is quicker and more effective than the primary response.

Memory cells can circulate for years and respond quickly after any subsequent encounter with the same antigen.

Antigens are any substance that the immune system can recognize and that can thus stimulate an immune response. B cells (B lymphocytes) are white blood cells that produce antibodies specific to the antigen that stimulated their production.

• naturally acquired active immunity.
• naturally acquired passive immunity.
• artificially acquired active immunity.

There are two types of adaptive responses: the cell-mediated immune response, which is carried out by T cells, and the humoral immune response, which is controlled by activated B cells and antibodies.

Unlike the innate immune system, which attacks only based on the identification of general threats, the adaptive immunity is activated by exposure to pathogens, and uses an immunological memory to learn about the threat and enhance the immune response accordingly.

Adaptive immunity It is characterized by specificity, immunological memory, and self/nonself recognition. The response involves clonal selection of lymphocytes that respond to a specific antigen. T cells and B cells are the two major components of adaptive immunity.

There are three important characteristics to adaptive immunity:

• Self-recognition (or recognition of non-self)
• Specificity.
• Memory.

There are four characteristics of adaptive immunity: antigenic specificity, diversity, immunologic memory and ability to distinguish between self and non-self. An immune response involves Lymphocytes (B-cells and T-cells) and antigen presenting cells (macrophages, B-cells, and dendritic cells).

The function of adaptive immune responses is to destroy invading pathogens and any toxic molecules they produce. Because these responses are destructive, it is crucial that they be made only in response to molecules that are foreign to the host and not to the molecules of the host itself.

Steps in adaptive immune process

• STEPS IN ADAPTIVE RESPONSE 1.Monocytes “eat” pathogen 2. Reveals part of antigen on cell surface 3. Receptor on helper T-cell identifies the antigen 4.
• STEPS IN ADAPTIVE RESPONSE 5. Killer T-cells become activated to attack specific pathogen 6.

Adaptive immunity can provide long-lasting protection, sometimes for the person’s entire lifetime. For example, someone who recovers from measles is now protected against measles for their lifetime; in other cases it does not provide lifetime protection, as with chickenpox.

The adaptive immune system works to protect and heal the body when the innate immune system fails. It provides the body with the ability to recognize and remember specific pathogens through their antigens.

The adaptive immune system is made up of: T lymphocytes in the tissue between the body’s cells. B lymphocytes, also found in the tissue between the body’s cells. Antibodies in the blood and other bodily fluids.

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in the body. The innate immune response is activated by chemical properties of the antigen. Adaptive immunity. Adaptive immunity refers to antigen-specific immune response.

Adaptive immunity is also referred to as acquired immunity or specific immunity and is only found in vertebrates. The adaptive immune response is specific to the pathogen presented. The adaptive immune response is meant to attack non-self pathogens but can sometimes make errors and attack itself.

A key feature of the adaptive immune system is memory. Repeat infections by the same virus are met immediately with a strong and specific response that usually effectively stops the infection with less reliance on the innate system.

One reason why the adaptive immune response is delayed is that it takes time for naïve B and T cells with the appropriate antigen specificities to be identified, activated, and proliferate. On reinfection, this step is skipped. The result is a more rapid production of immune defenses.

The humoral immune system deals with antigens from pathogens that are freely circulating, or outside the infected cells. Cellular immunity occurs inside infected cells and is mediated by T lymphocytes. The pathogen’s antigens are expressed on the cell surface or on an antigen-presenting cell.

The humoral immune response is mediated by antibody molecules that are secreted by plasma cells. Antigen that binds to the B-cell antigen receptor signals B cells and is, at the same time, internalized and processed into peptides that activate armed helper (more…)

cell-mediated immunity, so named because the T cells themselves latch onto the antigens of the invader and then initiate reactions that lead to the destruction of the nonself matter. B lymphocytes, on the other hand, do not directly attack invaders.

Cell-mediated immunity is an immune response that does not involve antibodies. Rather, cell-mediated immunity is the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

Cell-mediated immune responses involve the destruction of infected cells by cytotoxic T cells, or the destruction of intracellular pathogens by macrophages (more…) The activation of naive T cells in response to antigen, and their subsequent proliferation and differentiation, constitutes a primary immune response.

Also called cellular immunity. Compare antibody-mediated immunity.

Helper T cells (TH cells) also aid in cell-mediated immunity by releasing signaling molecules known as cytokines which can recruit natural killer cells and phagocytes to destroy infected cells and further activate TC cells; they do not directly destroy pathogens.

Nickel, certain dyes, and the active ingredient of the poison ivy plant are common examples. The response takes some 24 hours to occur, and like DTH, is triggered by CD4+ T cells. The actual antigen is probably created by the binding of the chemical to proteins in the skin.

The one exception to passive humoral immunity is the passive transfer of cell-mediated immunity, also called adoptive immunization which involves the transfer of mature circulating lymphocytes.