Sistema imunitário - parte II: fundamentos da resposta imunológica mediada por linfócitos T e B

Abstract

The immune system consists of an intricate network of organs, cells, and molecules responsible for maintaining the body's homeostasis and responding to aggression in general. Innate immunity operates in conjunction with adaptive immunity and is characterized by rapid response to aggression, regardless of previous stimulus, being the organism first line of defense. Its mechanisms include physical, chemical and biological barriers, cellular components, as well as soluble molecules. The organism first line of defense against tissue damage involves several steps closely integrated and constituted by different components of this system. The aim of this review is to restore the foundations of this response, which has high complexity and consists of several components that converge to articulate the development of adaptive immune response. We selected some of the following steps to review: perception and molecular recognition of aggressive agents; activation of intracellular pathways, which result in vascular and tissue changes; production of a myriad of mediators with local and systemic effects on cell activation and proliferation, synthesis of new products involved in the chemoattraction and migration of cells specialized in destruction and removal of offending agent; and finally, tissue recovery with restoration of functional tissue or organ.

Development of Dog Immune System: From in Uterus to Elderly

“…CD4 molecules on Th cells ligate MHC class II molecules used by APCs to present exogenous antigens. CD8 molecules on T cytotoxic lymphocytes bind MHC class I molecules that are used by infected or abnormal nucleated cells to present endogenous antigens [1,10]. MHC class I molecules are present in all nucleated cells, while MHC class II molecules are expressed only by APCs.…”

“…Co-stimulatory signals are required, namely the binding of CD40 and of CD80/CD86 presenting on APCs to its ligand, CD40L and CD28, on T cells, respectively. T cell stimulation by cytokines produced by APCs is also important to promote the immunological synapse [1,10].…”

Linfócitos T CD4+CD25+ e a regulação do sistema imunológico: perspectivas para o entendimento fisiopatológico da sepse

“…(6) Naïve CD4+CD25+ T cells are produced in the thymus in Hassall's corpuscles and are activated upon reaching the peripheral blood and secondary lymphoid organs, thereby acquiring the memory phenotype. (16) These cells represent approximately 5-15% of the CD4+ T lymphocytes in peripheral circulation. (17) The interleukin 7 (IL7) receptor (CD127), which is negatively regulated by the FoxP3 nuclear factor, is currently considered to be the most specific marker for identifying Treg among T lymphocytes and allows the identification of those with greater suppressive capacity.…”

Associação entre inflamação do tecido adiposo epicárdico e doença arterial coronariana: um estudo clinicopatológico

“…Todos os linfócitos T expressam CD3 38 , e um dos co-receptores mutuamente exclusivos (CD4 ou CD8) 33,39 . Os complexos associam-se com os receptores de células T (TCR) para formar um complexo proteico, que permite a transdução de sinal intracelular após o reconhecimento de epítopos, ligados a moléculas do complexo de histocompatibilidade (MHC) ou antígeno de leucócitos humanos (HLA), de uma célula apresentadora de antígeno 33 .…”

“…Os complexos associam-se com os receptores de células T (TCR) para formar um complexo proteico, que permite a transdução de sinal intracelular após o reconhecimento de epítopos, ligados a moléculas do complexo de histocompatibilidade (MHC) ou antígeno de leucócitos humanos (HLA), de uma célula apresentadora de antígeno 33 . Os linfócitos T só reconhecem antígenos processados e apresentados desta forma por uma célula apresentadora de antígeno 39 . Os receptores CD4+ e CD8+, auxiliares (T helper -Th) e citotóxicos, reconhecem um epítopo em associação com MHC, após a apresentação do antígeno e interação, ativando os linfócitos T. Uma vez ativados, é produzido uma ampla gama de respostas, incluindo a proliferação de células, secreção de citocinas e outros mediadores solúveis, e a expressão de moléculas de superfície 33 .…”