Protected class is a term used in United States anti-discrimination law. The term describes characteristics or factors which can not be targeted for discrimination and harassment. The following characteristics are considered "Protected Classes" and persons cannot be discriminated against based on these characteristics:

• Race - Federal: Civil Rights Act of 1964 and the Civil Rights Act of 1866
• Color - Federal: Civil Rights Act of 1964
• Religion - Federal: Civil Rights Act of 1964
• National origin - Federal: Civil Rights Act of 1964
• Age (40 and over) - Federal: Age Discrimination in Employment Act of 1967
• Sex - Federal: Equal Pay Act of 1963 & Civil Rights Act of 1964
• Familial status (Housing, cannot discriminate for having children, exception for senior housing)
• Sexual orientation (in some jurisdictions and not in others)
• Gender identity (in some jurisdictions and not in others)
• Disability status - Federal: Vocational Rehabilitation and Other Rehabilitation Services of 1973 & Americans with Disabilities Act of 1990
• Veteran status - Federal Vietnam Era Veterans Readjustment Assistance Act of 1974
• Genetic information - Federal: Genetic Information Nondiscrimination Act

Resources: http://en.wikipedia.org/wiki/Protected_class