T and B lymphocyte proliferation

T and B lymphocyte proliferation is a fundamental immunological process where these cells multiply in response to antigenic stimulation or other signals. This process is essential for mounting effective immune responses against pathogens and for developing immunological memory. T cell proliferation begins when a T cell recognizes a specific antigen presented by an antigen-presenting cell (APC) such as a macrophage. This recognition occurs through the T cell receptor (TCR) and triggers a cascade of signaling events[2]. Helper T cells coordinate both specific and nonspecific defenses largely by releasing chemicals that stimulate T cell and B cell growth and differentiation[2]. After activation, T cells undergo clonal expansion, followed by a death phase where approximately 90% of effector cells are eliminated by apoptosis[1]. B cell proliferation is initiated through B cell receptor (BCR) signaling, which is required for appropriate B cell growth, activation, proliferation, and differentiation[7]. The BCR signaling pathway involves multiple molecules including phospholipase C-gamma2 (PLC2), which generates second messengers that drive intracellular calcium release and activate protein kinase C (PKC)[7]. This leads to the activation of transcription factors such as NF-κB and NFAT, which are crucial for B cell activation, maturation, and survival[7]. Both T and B cell proliferation are regulated by complex signaling networks. The PI3K/Akt/mTOR pathway plays a critical role in controlling lymphocyte proliferation and differentiation[6]. Inhibition of mTOR by rapamycin blocks B cell proliferation and differentiation[6]. Similarly, PI3K inhibitors profoundly affect B cell proliferation[6]. Lymphocyte proliferation can occur through different mechanisms. Homeostatic proliferation is triggered by the availability of homeostatic factors and is influenced by the affinity of T cells for MHC-self-antigens[4]. Spontaneous proliferation, on the other hand, is triggered by the lack of memory T cells and is determined by the clonality of peripheral T cells[4]. Interestingly, activated B cells can suppress T cell function through metabolic competition. They can induce hypoxia in T cells by consuming more oxygen via increased oxidative phosphorylation (OXPHOS) and can deprive T cells of glucose through their high glycolytic activity[5]. This metabolic competition inhibits the mTOR pathway in T cells, resulting in suppression of T cell cytokine production and proliferation[5].

Other names

T cell expansionB cell expansionlymphocyte clonal expansion