Overview Introduction The immune system involves cells from two major lineages including login to view 11 more bullets These cells carry out many of the major roles of the immune system including login to view 6 more bullets Lymphoid Cells Lymphoid cells can broadly be divided into four classes including login to view 6 more bullets Lymphoid Cell Types Feature NK Cells B Cells Killer T Helper T Regulatory T Function Kill cells lacking MHC Secrete antibodies Kill infected cells Enable other immune cells Suppress immunity Surface proteins CD56 MHC receptor IL2 receptor CD19, 20, and 21 CD40 CD2 CD3 CD8 CD2 CD3 CD4 CD3 CD4 CD25 FOXP3 deficiency results inIPEX (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked) syndrome Secreted proteins Perforin Granzymes Antibodies Toxic compounds Diverse cytokines IL10 TGF-B Helper T-cells (CD4+ cells) can be further subdivided into classes based on function Helper T-Cell Subtypes Feature Th1 Th2 Th17 Function Promote cell based immunity Activate macrophages and cytotoxic T-cells Promotes humoral immunity Recruits eosinophils as part of parasite defence Involved in allergic responses Activate neutrophils Differentiation IFN-γ IL-12 IL-2 IL-4 IL-6 TGF-β Associations Granuloma formation Tuberculous leprosy Lepromatous leprosy IgE production by B cells Chronic inflammatory conditions Secreted Factors IFN-γ IL-2 IL-4 IL-5 IL-13 IL-17 IL-21 Myeloid cells Myeloid cells perform a large variety of innate immune functions including login to view 5 more bullets Different innate immune cells are specialized for different functions Myeloid Cell Types Cell Type Functions and Features Monocytes Phagocytosis of invading pathogens Differentiates into macrophages Express receptors for the antibody Fc and the complement protein C3b Macrophages Phagocytosis of pathogens as well as cellular debris Secretion of cytokines Stimulation of the healing response Dendritic cells Capture of antigens from pathogens Presentation of antigens to adaptive immune cells Called Langerhans cells in skin and mucosa Neutrophils Secretion of cytokines and signaling molecules Phagocytosis of pathogens Generation of reactive oxygen species Eosinophils Production of major basic protein Anti-parasitic defence Basophils Allergic response Mast cells Production and release of histamine Allergic repsonse