Human Immunity and Blood

T-cells are mainly confined to the paracortical (thymus-dependent) area of lymph nodes, and in nodes taken from children with selective T-cell deficiency. The paracortical region is virtually devoid of lymphocytes.

The granules contain a wide spectrum of microbicidal agents.

These terminal components form a complex, which inserts into the membrane to form a transmembrane ion channel, which leads to lysis of the cell.

Neutrophils are chemotactically attracted to the site of inflammation by C5a and mast cell chemotactic factors such as leukotriene B4.

This is the C3 convertase enzyme generated in the alternative complement pathway and is responsible for splitting off the small peptide C3a, leaving C3b as a residue.

Perforin inserts into the target cell membrane, thereby facilitating entry of TNF and granzymes into the target cell.

The respiratory, alimentary and genitourinary tracts are guarded immunologically by subepithelial accumulations of lymphoid tissues, which are not constrained by a connective tissue capsule. These may occur as diffuse collections of lymphocytes, plasma cells and phagocytes throughout the body and the lamina propria of the intestinal wall or as more clearly organised tissue with well-formed follicles as found in the Peyer's patches.

IgM is the first immunoglobulin class to be expressed on the surface of the developing B-cells, shortly followed by IgD. Early mature B-cells co-express IgM and IgD antibodies of identical antigen specificity.

Macrophages have an impressive range of functions, but appear unable to prime naive lymphocytes. This can be carried out by lymphoid interdigitating dendritic cells and cultured, but not freshly isolated, Langerhans' cells.

Lymphocytes are directly driven by antigen. The concentration of antigen is important because the binding to the surface of responding B-cells is necessary for continued stimulation. As the antigen concentration falls through catabolism or neutralisation or complex formation with antibody, the immune response diminishes. In this way, the immune response is not maintained at a high level when the antigen has been eliminated.

The middleman between blood and tissues is lymph.

Yes, it is correct. Mast cells acts as a secretory alarm cells of the body. Upon the slightest disturbance, they release chemical signals which diffuse through the surrounding ground substance and stimulate the process of inflammation.

Karl Landsteiner discovered the ABO system in 1900 and 1901, while trying to understand why blood transfusions sometimes saved lives and at other times caused death.

If they produced anti-A antibodies, it would destroy their own blood. However, they do normally produce anti-B antibodies since B type blood would be alien to them.

The Rh system apparently is genetically much more complex since it involves 45 different antigens on the surface of red cells that are controlled by 2 closely linked genes on chromosome 1. In most cases, the ABO system is controlled by only 2 antigens.