Alternative complement pathway and factor B activities in rats with altered blood levels of thyroid hormone

Evaluating the activity of the complement system under conditions of altered thyroid hormone levels might help elucidate the role of complement in triggering autoimmune processes. Here, we investigated alternative pathway (AP) activity in male Wistar rats (180 ± 10 g) after altering their thyroid hormone levels by treatment with triiodothyronine (T3), propylthiouracil (PTU) or thyroidectomy. T3 and thyroxine (T4) levels were determined by chemiluminescence assays. Hemolytic assays were performed to evaluate the lytic activity of the AP. Factor B activity was evaluated using factor B-deficient serum. An anti-human factor B antibody was used to measure factor B levels in serum by radial immunodiffusion. T3 measurements in thyroidectomized animals or animals treated with PTU demonstrated a significant reduction in hormone levels compared to control. The results showed a reduction in AP lytic activity in rats treated with increasing amounts of T3 (1, 10, or 50 µg). Factor B activity was also decreased in the sera of hyperthyroid rats treated with 1 to 50 µg T3. Additionally, treating rats with 25 µg T3 significantly increased factor B levels in their sera (P < 0.01). In contrast, increased factor B concentration and activity (32 percent) were observed in hypothyroid rats. We conclude that alterations in thyroid hormone levels affect the activity of the AP and factor B, which may in turn affect the roles of AP and factor B in antibody production.

Sheep erythrocyte sensitisation and restriction to lysis by the complement system from equine and sheep serum

Neste trabalho foi analisado o efeito do grau de sensbilizaçäo de hemácias de carneiro por anticorpo, na resistência à lise pelo complemento do soro equino e de carneiro. Os resultados mostraram que, à medida que houve um aumento do nível de sensibilizaçäo, ocorreu também um aumento da atividade do complemento homólogo, levando a 100 por cento de lise; o mesmo foi observado para o complemento do soro equino, geralmente considerado ineficiente na lise destas células. A restriçäo à lise pode, assim, ser sobrepujada por este tratamento. Estes dados podem ser de interesse para a compreensäo dos mecanismos envolvidos na modulaçäo do fenômeno de restriçäo, na saúde e em doenças envolvendo o sistema complemento em animais domésticos e no homem, bem como em diagnóstico laboratorial, onde säo utilizados ensaios hemolíticos para medida de atividade do complemento e pesquisa de anticorpos em amostras de soro