Acantholytic cells in Pemphigus are derived from -
First know about the layers of skin —


Epidermis (from superficial to deep) -
	Stratum corneum (Horny layer)
	Stratum granulosum (granular cells layer)
Stratum spinosum (Prickle cell layer)
	Stratum basale (Basal cell layer)
Dermis —
	Papillary dermis
	Reticular dermis


Pemphigus is characterized by acantholysis. Acantholysis is separation of epidermal cells from one another. This separation occurs due to antibodies (IgG) against the intercellular substances.
Acantholysis occurs in different layers of epidermis in different types of pemphigus.
Pemphigus vulgaris and ----> Acantholysis occur in between basal cells and cells of prickle cell layer (Stratum pemphigus vegetans spinosum). Some books also state that acantholysis occurs in suprabasal layer. Suprabasal layer is most probably, stratum spinosum as it is seen above basal layer
Pemphigus foliaceous and-- Acantholysis occurs in stratum granulosum.

Pemphigus erythematosus
So, Stratum spinosum is involved in pemphigus vulgaris and pemphigus vegetans and stratum granulosum is involved in pemphigus foliaceous and pemphigus etythematosus.
But, the answer should be stratum spinosum, as pemphigus vulgaris is the most common type of pemphigus and most probably they have asked about it.
Stratum granulosum
Stratum basale
Langerhans cell
Stratum spinosum