Reference

In ataxia-telangiectasia (A-T) patients, several immunological abnormalities are observed, which include:

1. Lymphopenia: A reduction in the number of lymphocytes, which are crucial for the immune response.
2. Impaired Cellular and Humoral Immunity: Dysfunction in both cellular immunity (T cells) and humoral immunity (B cells) due to abnormal T, B, and NK cells.
3. Low Total Immunoglobulin Levels: Hypogammaglobulinemia, with low levels of IgG, IgA, or IgM.
4. Defective Antibody Response: Particularly to polysaccharide antigens, leading to recurrent infections.
5. Decreased Peripheral Lymphoid Tissue: Reduced lymphoid tissue affects the immune system's ability to mount an effective response.
6. Increased Susceptibility to Infections: Predisposition to bacterial infections, especially of the respiratory tract.
7. Autoimmune Disorders: An increased risk of developing autoimmune diseases.
8. Chromosomal Instability: Which can affect the function of immune cells.
9. Immunoglobulin Deficiencies: Commonly affecting IgG4, IgA, IgG2, IgE, and IgG.

These abnormalities contribute to the immunodeficiency observed in A-T patients, leading to increased susceptibility to infections and complications. The images provided in the search results further illustrate the clinical manifestations and immunological aspects of ataxia-telangiectasia. For more detailed information, refer to the sources such as PubMed Central, the Immune Deficiency Foundation, and ScienceDirect.