Cooperation of blood and connective tissue cells against noxious agents
After description of the all connective tissue components we can more detail consider two functions of the loose connective tissue - protective and plastic functions.
Protection against noxious agents (different infections, antigens, bacteria and others) is provided by cooperation of blood and connective tissue cells against noxious agents.
Each outside noxious substance (foreign material) calls in the human body local reaction, named inflammation (or immunological reaction) in which the cells of the blood and connective tissue are mobilised to bring the destruction of the foreign substance and the repair of the damage.
As you have already known all leukocytes are always present in the connective tissue.
In inflamed connective tissue (in any places of the body) leukocytes in great number migrate from the venules at the beginning of the process.
The process of the defence begins from the T-lymphocyte, that modifies a developing immune response by releasing non-specific signals to which other T-lymphocytes respond.
So T-lymphocyte is the first cell which identificates each noxious agent as foreign to the body, because it carries histocompatible molecules on its surface and can differentiate into several types of T-lymphocytes.
-If the noxious agents are transplanted or tumor cells, the T-lymphocyte transforms into Killer cell, which with the cytotoxic matters kills that grafted, swell cells.
- In other cases T-lymphocyte differentiates into T-lymphocyte-helper, which induces non-specific reaction of B-lymphocyte. Under the T-lymphocyte induction B-lymphocyte is converted into plasma cell produces substances called antibodies (immunoglobulins), which can destroy foreign bodies.
T-lymphocyte also transmits the information to the macrophage. The functions of the macrophage are as follows: non-specific phagocytosis, killing of ingested microorganisms, digestion and presentation of antigens to B-lymphocyte. So, the T-lymphocyte and macrophage both induce the B-lymphocyte to be transformed into the plasma cell which produce antibodies are specific for this concrete antigen. Other words, the plasma cell specific respond is possible only after the macrophage presentation.
T-lymphocyte also differentiates into T-lymphocyte-supressor for B-lymphocyte. T-helper and T-supressor work together adding each other.
And there are T- and B-lymphocytes ‘memory’, which have a specific memory for the concrete antigen, which provides their subsequent behaviour when organism will be exposed at a late time to the same antigen.
Further macrophage induces the work of the other cells, which are present in the connective tissue.
Microphage induces mast cell (basophilic leukocyte) thus calls the degranulation and the histamine and heparin are released from mast cell. Histamine increases of vessels permeability, dilates blood vessels and produces oedema (swell), that's why many leukocytes migrate from the blood to the inflamed place. Heparin is an anticoagulant of the blood, which prevents blood clotting.
Migrated leukocytes:
Neutrophilic leukocyte functions as microphagocyte, which swallows up the debris of dead leukocytes and small infections.
Eosinophil is necessary for the utilisation of heparin and histamine and increases in number following parasitic infections or allergic reactions. Their mane function is the phagocytosis of antigen-antibody complexes, formed during allergic reactions.
Basophil fucntions as mast cell.
And T- and B-l-scome here in additional amount and work as usually.
· Microphage induces the connective tissue cells properly. Fibroblasts is induces for capsule construction around the inflamed place for insulation of infection.
· Macrophage induces the fat cells, which are the source for energy to all cells in inflamed place.
· Macrophage induces the pigment cells for the utilization of wastes of adrenaline from nerve endings and histamine and heparin.
Note the following: elevation or depression of the levels of certain classes of leukocytes is related to specific diseases.
E. g. in person infected with the AIDS (acquired immunodeficiency syndrome) by VIH (immunodeficiency virus) - the number of T helper cells is dramatically reduced.
Now more detailed description of the forth function of the connective tissue - the regenerative capacity of the connective tissue, or repair after injury (plastic function). This function is provided by fibroblasts respond to injury by fibrogenesis.
Fibroblasts are involved in the healing of defects not only in the connective tissue, but also in other tissues, that have little or no regenerative capacity of their own.
E.g. a connective tissue fibrous scar replaces the heart muscle that degenerates following a heart attack. The same regeneration provided by connective tissue happens in all tissues and in different organs, or in skin.