. 2019 Sep 17;20(18):4588. doi: 10.3390/ijms20184588

Table 1.

HSPs Found Extracellularly, in Exosomes and on Membranes.

Subfamily Name	Prototypical Members	Exosome HSP	Free HSP	Membrane HSP
HSP90	Hsp90α ^HSP90AA1 Hsp90β ^HSP90AB1 Gp96 ^Grp94/Hsp90B TRAP1 ^Hsp75/Hsp90L	Cancer [1] B cell [6]	3D Tumoroid [5] HDF [9]	Tumor cells APCs Infected erythrocyte [10,11,12]
HSP70 HspA(1-12)	Hsp72 ^{HspA1A/HspA1B} Hsc70, BiP ^HspA5 Hsp70B’ ^HspA6 See [2] in detail	Cancer [1,13] B cell [6]	Mφ [14], Cancer [5,15] Exercise [16] Sarcopenia [17]	Cancer [18,19]
Small HSP HspB(1–10)	Hsp27 ^HspB1 αB-crystallin ^HspB5	B cell [6], Sera, body fluids [8]	Sera, body fluids [8]	?
Large HSP	Hsp105, Hsp110 Grp170 ^Orp150	Cancer [1]	?	?
HSP40 DnaJ	Tid1^DnaJA3 [20] ERdj4 ^DnaJB9 RME8 ^DnaJC13	?	?	?
HSP47	Colligin-2 ^RA-A47	?	RA sera [21]	Chondrocyte [22]
Chaperonin	TRiC ^CCT Hsp60, Hsp10	Cancer [1,23]	DM [24]	?

Cell damages in pathological conditions induce expression and release of inducible types of HSPs, often found in extracellular space as free forms, on the membrane surface, and in vesicles, although constitutively expressed types of HSP is also found extracellularly. ?, unknown; RA, rheumatoid arthritis; DM, diabetes mellitus; HDF, human dermal fibroblast; APC, antigen-presenting cell.