Immunology primer for neurosurgeons and neurologists part I: Basic principles of immunology

Abstract

Our knowledge concerning the workings of the immune system has evolved considerably over the past 20 years, with great strides being made as regard to complex interactions and repertoire of effector reactions under a host of conditions. Many of our previous understandings have been challenged, especially concerning tumor immunology and autoimmunity. Also of critical importance is our understanding of how the immune system terminates its attacks and the mechanisms used to regulate the balance between proinflammatory and antiinflammatory mechanisms, so as to prevent excessive immune bystander damage. I will discuss in part I the basic physiology of innate immune function and the immune systems reactions to invasion by microorganisms.

Keywords: Adaptive immunity; cell-mediated immunity; cytokines; innate immunity.

Figure 1

Overview of the immune system, demonstrating the major components of the innate and adaptive immune components

Figure 2

Development of T-lymphocytes in the thymus gland including the various stages of maturation and differentiation

Figure 3

Stages of B-cell differentiation and maturation from bone marrow stem cells

Figure 4

Processes involved in differentiation and proliferation of a dendritic cell as an antigen presenting cell [APC]. Once the dendritic cell has been activated, it interacts with the T-lymphocyte within the lymphoid tissue so as to generate activated CD4 T-Helper cells

Figure 5

Pattern Recognition Receptor types and basic functions

Figure 6

Toll-Like Receptors [TLRs] demonstrating subtypes and their major antigen agonists

Figure 7

Demonstration of cell signaling processes involved in both membrane TLRs and endoplasmic TLRs

Figure 8

Basic process of T-lymphocyte activation by exposure to an APC and IFN-γ . A number of cytokines are involved in the activation process

Figure 9

Demonstration of the classification of Th1 and Th2 helper T-cells and their functions in controlling immune reactivity

Figure 10

Major Histocompatibility Complex Class 1 [MHC class I] is a surface receptor that plays a vital role in immune cell responses and plays a central role in self-identification. By binding peptides derived from the cytosol and presenting them to CD8+ lymphocytes, the MHC class I allows the lymphocytes to determine if the peptide if of self and to be ignored or foreign and to be attacked

Figure 11

Major Histocompatibility Complex Class II [MHC class II]. When immune cells, such as macrophages and microglia [APCs] are activated, MHC class II complexes with invading extracellular peptides and these in turn interact with lymphocytes, such as the CD4+ T-cell

Figure 12

Demonstration of the interaction between macrophages and cytokines, which can trigger a switching from a classical cytotoxic active macrophage (M1) to the alternative pathway, producing an immune suppressant macrophage phenotype (M2)