Our current understanding of humoral immunity of poultry.

With the inception of the modem era of avian immunology in the mid-1950s following the discovery of the role of the bursa of Fabricius (BF), steady and persistent research has been conducted by scientists. Findings that have advanced our knowledge of humoral immunity (HI) include the distinct role of B cells in antibody production, explanation of antibody diversity by gene rearrangement and conversion, identification of a bursal secretory dendritic cell and dendritic cells of the spleen, characterization of cytokine factors, and mapping of MHC class II genes. Numerous experiments have been conducted to evaluate the HI responses of poultry through antibody titer determination and quantitation of immunoglobulin concentrations in the humors. Antibody studies have included the genetics of HI regarding both quantity and persistence of responses as influenced by multiple genes and MHC haplotypes. In the past decade, emergence of monoclonal antibody reagents to identify cell surface markers on B cells and accessory cells has allowed for discrimination of HI functions of cells by immunohistochemistry, flow cytometry, and other techniques. The signaling mechanisms of avian B cells are becoming better understood. Continued work in avian immunity has led to more advances in identification, characterization, and gene sequencing of important cytokines. Additional work is required to identify and sequence genes for many more cytokines that have direct effects on B cells. A brief history of research published on avian B cells is presented with an examination of some of the important research findings reported in recent years.