When it comes to tumors, Immunological diagnosis of foreign antigens consists of humoral mechanisms like antibodies and cellular mechanisms. Now although most humoral responses cannot prevent further tumor growth, effector cells like T cells have effective tumoricidal abilities. This rather fancy term means they can destroy tumor cells.
Effector cell activity is inducted by other cells that present tumor-specific antigens or tumor-associated antigens on their surface. These cells are referred to as antigen-presenting cells and are supported by cytokines.
Cytokines affect the growth of all blood cells as well as other cells that help the boy’s immune and inflammation responses. In an immunoassay test for tumors, they boost anti-cancer activity by sending signals that help kill abnormal cells and elongate the lifetime of normal cells.
Despite the efforts of effector cells, host response immunoreactivity may fail to control tumor occurrence and growth. A lot goes on in immunological diagnosis for tumors so let’s dive right in.
Remember the T cell I just mentioned? They are the primary cells responsible for the direct recognition and killing of tumor cells. They carry out immunologic surveillance and then annihilate newly transformed tumor cells after identifying tumor-associated antigens.
The T-cell response to tumors is modulated by other cells of the immune system. Some cells require the presence of humoral antibodies directed against the tumor cells to initiate the interactions that eventually lead to the death of tumor cells. In contrast, suppressor T cells inhibit the immune response against tumors.
Natural Killer Cells
These cells are another population of effector cells with tumoricidal abilities. They don’t have the receptor for antigen detection but can still recognize normal cells infected with viruses or tumor cells. Their tumoricidal abilities are termed as natural precisely because it is not inducted by a specific antigen. The mechanism by which these NK cells discriminate between normal and abnormal cells hasn’t been quite yet discovered – it’s still under study.
Evidence suggests that class I MHC molecules on the surface of normal cells inhibit NK cells and prevent lysis. Thus, the decreased levels of class I molecule expression characteristic of many tumor cells may allow activation of NK cells as well as subsequent tumor lysis.
Cytotoxic T lymphocytes
CTLs recognize antigens on target cells and lyse these cells. I know you’re probably wondering what lyse means. Well, me too. Lysis, the process, is the disintegration of a cell by rupturing the cell wall or cell membrane for that matter.
The antigens may be cell surface proteins or maybe intracellular proteins like TAAs. TAA is short of tumor-associated antigens. These TAAs are expressed on the surface in combination with class I major histocompatibility complex molecules. Immunoassay tests for tumor-specific CTLs are accurate in:
- Kidney carcinoma
- Breast carcinoma
- Colon carcinoma
Regulatory T Cells
These T cells are normally present in the body and help prevent autoimmune reactions. They are produced during the active phase of immune responses to pathogens and limit strong immune responses that could damage the host. Accumulation of these cells in cancers inhibits antitumor immune responses.
They are produced by immune cells to stimulate growth or induce activities of other immune cells. Such lymphokines include (IL-2) also known as T cell growth factor and IL-12 produced by dendritic cells and specifically induces CTLs enhancing antitumor immune responses.
Speaking of dendritic cells:
They are dedicated antigen-presenting cells present in barrier tissues like the skin and lymph nodes. They play a key role in the initiation of the tumor-specific immune response. These cells take up tumor-associated proteins, process them and then present the TAAs to T cells to stimulate the CTL response against the tumor. Different classes of these cells can mediate tumor promotion or suppression.
That just about covers immunological diagnosis in tumors although it is a rather large field.