The body initiates an immune response to danger signals. The Danger model of the immune system postulates that danger signals are produced by exogenous molecules from foreign invaders, such as bacteria, and endogenous molecules released from damaged or injured cells. The response involves antigen recognition leading to up-regulation of cytokines and cell surface markers, followed by the recruitment of antigen presenting cells and T-helper cells which determine how the immune system responds. Endogenous danger signals include Hsp72 and HMGB-1. This thesis describes the development of specific antibodies and ELISAs for use in the quantification and detection of intra-cellular Hsp72 from cell extracts, and released Hsp72 from cell cultures which enabled the confirmation of physiological levels of Hsp72 from model systems. The ability of endogenous Hsp72 to stimulate an immune response was demonstrated and this response was not solely due to LPS contamination of recombinant protein preparations. Hsp72 was able to augment the response to LPS. In the presence of another endogenous danger signal, HMGB-1, relative amounts of Hsp72 were shown to augment a pro-inflammatory response whilst being able to maintain an anti-inflammatory response demonstrating Hsp72 has the ability to modulate the immune response. Hsp72 was also shown to be able to stimulate an immune response by binding to cell surface receptors, which could be blocked by specific peptides corresponding to known receptors. These include some receptors not utilised by LPS. The proportion of these different danger signals has consequences for the progression and outcome of an immune response and this may well be modulated by imposition of a supplemental or future stress at different points. In the most severe case, this can lead to death through sepsis following trauma.