text: Antibodies serve various functions in protecting the host against the pathogen. Their soluble forms which carry out these functions are produced by plasma B cells, a type of white blood cell. This production is tightly regulated and requires the activation of B cells by activated T cells (another type of white blood cell), which is a sequential procedure. The major steps involved are:
  *Specific or nonspecific recognition of the pathogen (because of its antigens) with its subsequent engulfing by B cells or macrophages. This activates the B cell only partially.
  *Antigen processing.
  *Antigen presentation.
  *Activation of the T helper cells by antigen-presenting cells.
  *Co-stimulation of the B cell by activated T cell resulting in its complete activation.
  *Proliferation of B cells with resultant production of soluble antibodies.