Lymphocyte Activation and Cytokine Production in Autoimmune Hemolytic Anaemia (AIHA)

Abstract

We studied 16 patients affected by autoimmune hemolytic anaemia (AIHA), both idiopathic and associated with other diseases (B and T lymphoma, B hepatitis, gastric carcinoma, systemic lupus erythematosus) or a-methyldopa therapy, in order to value T- and B-cell activation. We determined the count of T- and B-cell subsets in peripheral blood, the proliferative response of peripheral blood lymphocytes (PBL) to phytohe-magglutinin (PHA) and to pokeweed mitogen (PWM), the percentage of CD25 ⁺ cells in culture and interleukin (1L)-lα, IL-2, IL-4, tumor necrosis factor (TNF)α and soluble IL-2 receptor (sIL-2R) levels in sera and in culture. Except for an increase in CD4 ⁺ and CD8 ⁺ T cell number in a case of AIHA associated with a T lymphoma and an increase in the percentage of CD5 ⁺ and PCAl⁺ B cells in two cases of AIHA associated with B lymphoma and with SLE, no further data showed a relationship with the disease possibly associated with AIHA, so both idiopathic and secondary AIHA cases were analyzed together. CD4 ⁺ T cells were reduced in number in 9 cases, while CD8 ⁺ T cells were reduced in 6 cases. The percentage of CD5 ⁺ B cells was increased in 5 cases. The percentage of PCAl⁺ cells was increased in all cases (mean ± sd: 18 ± 22 vs 0,2 ± 1 in controls). The average PBL proliferative response to PHA was reduced (S.I. 71 ± 55 vs 138 ± 45 in controls) as well as that to PWM (S.I. 27 ± 21 vs 75 ± 24 in controls), despite IL-2 high levels, in all cases, in both sera (meanfsd: 648 ± 351 pg/ml vs 16 ± 4 pg/ml in controls) and culture supernatants (meanksd: 1045 f 677 pg/ml vs 195 ± 51 pg/ml in controls). In PHA stimulated cultures the percentage of CD25⁺ cells was reduced (meanasd: 37 ± 18 vs 63 ± 14 in controls), sIL-2R levels were like controls in 7 cases. In sera sIL-2R levels were increased in all cases (meanfsd 1256 ± 465 U/ml vs 256 ± 114 U/ml in controls), IL-lα was increased in all cases too, while IL-4 levels were increased only in 7 cases. Linear regression analysis generally showed a low relationship between S.I. and IL-2, IL-4 and sIL-2R levels in supernatants of PHA stimulated culture as well as between S.I. and the percentage of CD25 ⁺ cells. Taken together these data suggest a state of B- and T-cell hyperactivation in AIHA. The low PBL proliferative response in vim, explained in previous studies as a temporary functional exhaustion, might be itself a sign of the complete lymphocyte activation occurring in vivo in AIHA.

Key Words:

• lymphocyte activation
• cytokines
• autoimmune hemolytic anaemia