More correctly, monoclonal antibodies can be defined as hybrid homogeneous proteins, obtained from a single engineered lymphocyte clone.
Monoclonal antibodies are widely used in the clinical setting, both for diagnostic and therapeutic purposes.
However, before delving into the uses of these particular proteins and to better understand their mechanism of action, it may be useful to have a brief introduction on what antibodies are.
. These proteins are able to recognize and bind specifically to other types of substances defined as "antigens" (antigens can be of various nature; for example, protein, polysiccaridic, lipidic, etc.).
The function of antibodies is to recognize and neutralize foreign agents and / or pathogens, such as, for example, viruses, bacteria or toxins. This is possible thanks to the particular structure of these molecules.
In fact, antibodies are globular proteins with a particular "Y" conformation. Within this protein structure there are a so-called constant region and variable regions, corresponding to the arms of the "Y". It is precisely at the level of the variable regions that the specific binding sites for the antigen are found.
Each B lymphocyte is capable of producing millions of antibodies, in turn capable of recognizing different types of antigens (polyclonal antibodies).
Once the antibody binds to the antigen for which it is specific, the antibody itself is activated and gives rise to the immune response that will lead to the elimination of the foreign agent.
towards the target of interest, avoiding to involve other parts of the organism as well. In this way, it is possible to potentially reduce unwanted effects and increase the probability of therapeutic efficacy.
The conjugation of radioactive isotopes to monoclonal antibodies, on the other hand, is a technique that is mainly used in anticancer therapy. More precisely, in these cases we speak of radioimmunotherapy (for more detailed information on this, see the "dedicated article" External Radiotherapy and Internal Radiotherapy ").
A further classification of monoclonal antibodies can be made according to the use made of them. In fact, as mentioned, these particular glycoproteins can be used both for diagnostic purposes and for therapeutic purposes.
Monoclonal Antibodies used in the Diagnostic Field
As you can easily guess, this type of monoclonal antibodies is used to diagnose the presence of a certain antigen and, if necessary, even to measure its quantity.
Monoclonal antibodies, therefore, can be used to detect bacterial or viral agents, particular types of proteins or cells and tumor markers.
It is therefore clear how these molecules can be exploited in clinical laboratories for the diagnosis of pathologies (such as, for example, neoplasms), but not only. In fact, the monoclonal antibodies used in this field are also widely used in the so-called diagnostic kits for home use, such as, for example, the well-known pregnancy tests and ovulation tests.
Monoclonal Antibodies used in the Therapeutic Field
There are different types of monoclonal antibodies to be used for therapeutic purposes, as are the targets of therapy and the pathologies for which these molecules are used.
To try to simplify the concept as much as possible, we can divide these active ingredients according to the activity they perform:
- Monoclonal antibodies with anti-inflammatory action: drugs such as infliximab (Remicade®, Remsima®, Inflectra®) and adalimumab (Humira®) belong to this group. These monoclonal antibodies exert an "anti-inflammatory action since their antigen is constituted by human TNF-α, one of the pro-inflammatory cytokines most involved in the symptomatology of inflammatory diseases on an autoimmune basis, such as, for example," rheumatoid arthritis and "psoriatic arthritis. .
- Monoclonal antibodies with immunosuppressive action; the target of these active principles is mainly constituted by defense cells such as B lymphocytes and T lymphocytes and by proteins fundamental for their differentiation and activation, such as interleukin-2.
The drugs used in the treatment of autoimmune diseases and in the prevention of rejection in organ transplants belong to this group of monoclonal antibodies, including rituximab (also used in the treatment of some types of lymphomas) and basiliximab (Simulect®).
In addition, omalizumab (Xolair®) also belongs to this group, the target of which is human IgE and is used in the treatment of allergic asthma. - Monoclonal antibodies with antitumor action; there are numerous active ingredients belonging to this group. The target of these monoclonal antibodies is mostly constituted by factors fundamental for the development of malignant cells, or by proteins that are overexpressed when certain types of tumors are present, as is the case, for example, in the case of HER-2 positive breast tumors. In this case, the monoclonal antibody trastuzumab (Herceptin®, Kadcycla®) is used for the treatment of this tumor form. Rituximab (MabThera®), cetuximab (Erbitux®) and bevacizumab (Avastin®).
Furthermore, there are monoclonal antibodies capable of exerting activities different from those just described. This is the case of abciximab (Reopro®), which is endowed with antiplatelet activity. The antigen of this monoclonal antibody is, in fact, the glycoprotein IIb / IIIa present in platelets and involved, in fact, in the processes of platelet aggregation.
