Medical Science Test 2 Nddc Scholarship

Bruton's agammaglobulinemia (X-linked agammaglobulinemia) is a genetic disorder where B-cells fail to mature properly. This leads to a severe deficiency of all classes of immunoglobulins (antibodies), making the patient highly susceptible to recurrent bacterial infections. Job's syndrome is an IgE disorder, and Chronic Granulomatous Disease affects phagocyte function rather than B-cell production.

Antinuclear antibodies (ANA) are the hallmark diagnostic marker for SLE, with a sensitivity of about 95%–99%. These antibodies are directed against the contents of the cell nucleus. While not exclusive to Lupus, a negative ANA test makes a diagnosis of SLE very unlikely. Anti-histone antibodies are more specifically linked to drug-induced lupus, and anti-microsomal antibodies are associated with thyroiditis.

The TB skin test (Mantoux test) is a classic example of Type IV or Delayed-Type Hypersensitivity (DTH). Unlike immediate reactions (Type I), this response is mediated by T-cells rather than antibodies. It takes several days to develop because it involves the recruitment and activation of macrophages and T-cells at the site of the injection.

Interleukin-1 (IL-1) is a pro-inflammatory cytokine produced mainly by macrophages and monocytes. It plays a central role in the immune response by inducing fever, activating T-cells, and stimulating the production of other inflammatory mediators. IL-2 and IL-4 are primarily produced by T-cells, and IL-3 is a hematopoietic growth factor.

IgG and IgM are the only classes of immunoglobulins capable of activating the classical complement pathway. IgG (specifically subclasses IgG1 and IgG3) binds to the C1 component of complement once it has attached to an antigen. This leads to a cascade that results in the destruction of the pathogen. IgA, IgD, and IgE do not have this capability.

Cytotoxic T-cells are characterized by the presence of the CD8 glycoprotein on their surface. CD8 acts as a co-receptor that recognizes the MHC Class I molecules found on almost all nucleated cells in the body. This allows Cytotoxic T-cells to identify and kill cells that are infected with viruses or have become cancerous. CD4 is the marker for Helper T-cells.

T-cells (cell-mediated immunity) are specifically geared toward killing infected cells (viruses, TB) or foreign organisms (fungi). Toxins, such as those produced by tetanus or diphtheria bacteria, are extracellular molecular threats. These are primarily targeted and neutralized by antibodies (humoral immunity) produced by B-cells, rather than by the direct action of T-cells.

Oligodendrocytes are the myelin-producing glia of the Central Nervous System (CNS), which includes the brain and spinal cord. A single oligodendrocyte can provide myelin for several different axons. In the Peripheral Nervous System (PNS), this same function is performed by a different type of cell called the Schwann cell.

Schwann cells are the primary glial cells of the Peripheral Nervous System (PNS). Unlike oligodendrocytes in the CNS, a single Schwann cell typically wraps around only one segment of a single axon. They are crucial for the rapid conduction of nerve impulses in nerves outside the brain and spinal cord.

Astrocytes are star-shaped glial cells that are the most numerous cell type in the central nervous system. They perform a vast array of essential functions, including maintaining the blood-brain barrier, providing structural support, regulating the chemical environment of the extracellular space (especially potassium levels), and providing metabolic support to neurons. While oligodendrocytes (oligocytes) are also common, astrocytes outnumber them and play a more diverse role in general CNS homeostasis.