ABSTRACT
Because MDS is a clonal disorder that most often, but not always [2], affects lymphohematopoietic progenitor cells at various stages of differentiation [3,4], lymphoid cells may be derived from the malignant clone [5-7]. Most frequently, the B cells are clonal, but cases with involvement of T cells have been reported [5]. Alterations of the immune system are frequently observed [8], including a peripheral blood lymphocytopenia with reduced numbers of CD4 T cells [9]. T cells may show reduced response to mitogens [10], B cells may have deficient receptors for C3d [II], and the serum levels of soluble IL-2 (interleukin-2) receptors can be increased [12]. Activity of natural killer cells may be reduced with failure to respond to IF (interferon) and deficient IF production [13]. Lymphoid and plasma cell neoplasias not infrequently coexist in MDS patients [14]. A third of the patients can have a polyclonal rise in serum immunoglobulin levels, and in 12% of MDS patients a coexisting monoclonal gammopathy has been found [15]. In 19% of cases, the serum immunoglobulin levels were reduced [15]. Autoantibodies were most frequently found in patients with CMML [15,16]. The significance of the immunological abnormalities is still not clear, whether they are age-related changes also found in elderly patients without MDS. whether they are due to repeated infections frequently occurring in MDS patients, whether they occur secondary to abnormal macrophage function, or lastly whether they are due to the clonal origin of the lymphoid cells [17].
