Basic Concepts of Immune Response and Defense Development

Abstract

The induction of immune responses requires critical interaction between innate parts of the immune system, which respond rapidly and in a relatively nonspecific manner, and other specific parts, which recognize particular epitopes on an antigen. A critical element in this interaction is the role played by dendritic cells (DCs), which represent "professional antigen-presenting cells." DCs endocytose and process antigen to peptide presented on the cell surface in association with major histocompatibility complex (MHC) molecules. This presentation results in interaction with and stimulation of helper T (Th) lymphocytes, which recognize peptide in association with either MHC class II or cytotoxic T (Tc) lymphocytes, which recognize peptide in association with MHC class I. Stimulation of Th lymphocytes produces the growth and differentiation factors (cytokines) essential for the B lymphocytes that have responded to a more intact form of the antigen and that differentiate into antibody-producing cells. The precise interaction between the cells depends on cognate ligand-receptor recognition between the B and Th lymphocytes. DCs also play a direct role with the stimulation of the B lymphocytes. It appears that DC can deliver antigen to the B lymphocytes in a more intact form than the processed form essential for stimulating T lymphocytes, and can release cytokines that assist the differentiation of the B lymphocytes into antibody-producing cells. This close relationship among the three cell types and the cytokines that are produced ensures the precise control and regulation necessary for immune response development.

Schistosoma mansoni Triose Phosphate Isomerase Peptide MAP4 is Able to Trigger Naïve Donor Immune Response Towards a Type‐1 Cytokine Profile

“…This innate APC response dictates whether the ensuing adaptive CD4 + T helper (Th) cell responses will be proinflammatory and Th1 type or anti-inflammatory and Th2 type [1][2][3][4][5][6][7]. APC are activated when pathogens or antigens bind to cell surface receptors, which include numerous C-type lectin receptors, the Toll-like receptors, scavenger receptors and others [8,9].…”

Expression of CCL20 and Granulocyte-Macrophage Colony-Stimulating Factor, but Not Flt3-L, from Modified Vaccinia Virus Ankara Enhances Antiviral Cellular and Humoral Immune Responses

“…MVA has been shown to abortively infect professional antigen-presenting cells (APCs), including dendritic cells (DCs), B cells, and macrophages (14; unpublished data), cells that play central roles in eliciting antiviral immune responses by mediating effective direct and cross-presentation of microbial antigens to naïve CD4 ϩ and CD8 ϩ T cells in the secondary lymphoid organs to initiate adaptive antiviral immune responses (4,12,16,27,31,45,51,70). However, the immunogenicity of MVA is likely limited, despite its tropism for APCs, because of an inability to replicate in mammalian hosts that restricts viral gene (antigen) expression to cells infected at the site of immunization.…”

Injection site‐dependent induction of immune response by DNA vaccine: comparison of skin and spleen as a target for vaccination

“…Two types of plasmid DNA, pCMV‐OVA and pPep‐ER, which mainly undergo cross‐presentation and direct‐presentation pathways, respectively, were used as vaccines. Generally, the generation of antibody is associated with helper T cells 26, which recognize and are activated by MHC class II molecule‐antigen complex presented by APCs. Therefore, immunization with pCMV‐OVA or OVA in CFA, both of which possess MHC class II epitopes, is able to induce anti‐OVA antibody.…”