**3.3 Heat shock proteins**

Heat shock proteins (HSP) are a type of stress-inducible protein that are present in all organisms [70] and their cells at low levels in normal physiological conditions. They have been functionally linked to cell apoptosis, protein homeostasis, cell growth mediation as play an important role during fertilization [70–76]. HSPs also function as chaperones, and act in protein assembly and unfolding. Various member of the HSP family have been postulated to have roles in antigen presentation and as a chaperones of peptides to major histocompatibility complex class I and class II [75, 76]. HSPs are typically classified into five subunits or families according to their molecular weight; Large HSP (HSP110, glucose-regulated protein 170), HSP90, HSP70, HSP60 and small HSPs (HSP27, HSP40). Significant research has focused around the role of HSPs in disease progression and on their role as therapeutic targets and as biomarkers.
